As far as size goes, as the title suggests, these are TINY. There's few LEDs on the mass market that are smaller, but these are ready to use. For those like me without micro-soldering abilities, these are excellent. Handling them in any way requires a lot of gentle care. The leads are super fine and I would assume fragile. They are not as fragile as I assumed, and learned during one particular insertion that they are tougher than they look. The LED assembly is also very, very small. I found it took extra care to uncoil them for use, and a third hand tool with padded jaws is perfect for keeping them untangled during installation. I built my signal kits with a ¼” of so extra mast tube protruding below the foundation/base. That will be useful for the final install step.

As to installing them in the signal, a bit of pre-install prep is necessary to make things easier later. If you have painted the signal (and even if you haven't), paint the interior of the signal head and sunshade with flat back paint of your choice and allow to dry. It will be almost impossible to paint the interior of the head and sunshades after installing the LED without getting paint on the LED (counterproductive). Painting the interior of the head blocks out stay light from entering, is more prototypical and that's the whole idea of using this high caliber of products on your model railroad. Ensure your paint work has not plugged the pre-filed and drilled mast entry holes. I used a #76 drill to clean the hole out and ensure smooth lead wire insertion.

Installing these LEDs into the signals (I HIGHLY recommend the Showcase Miniatures searchlight signal kits) is not a picnic. It will be frustrating at first, but you'll soon learn how to manipulate the leads efficiently. I will say the tips and tricks Debbie graciously provided (also noted below) were essential to success, but I developed a couple of my own. Third hand tools are a necessity! Strong magnification is also essential if you have older eyes.

1. Clamp your assembled signal mast tube into the padded jaws of your third hand tool, facing cutout up (I positioned my wire cutout on the ladder side per my prototype). Padded jaws prevent marring or mangling the mast tube, especially if you have painted or decorated the signal. Handholding to install the leads is nearly impossible without a second person, and a third hand tool doesn't move (too much). Installing two LEDs in a single mast IS possible. The third hand tool is vital for these especially.

2. Uncoil the leads, taking great care to avoid kinking them and GENTLY pull them taut and straight. Using a fresh 9-volt battery and a resistor per the LED instruction, ensure each color illuminates properly. One can use the testing period to dial in the resistor strength/setting for desired brightness. Once satisfactorily tested, you are ready to install.

3. With the LED secured by the leads in another padded third hand clamp, bundle the wires together and ensure they are all evenly taut without loops or excess lead material bulging out/birdcaging, and cut them evenly the same length. A sharp hobby knife blade works great for this. Chuck them evenly into a pin vise/drill, secure the chuck, and gently hand twist the drill to evenly twist about 3-4” worth of the leads. I found twisting the leads as I would larger electrical wire (by hand) was wholly ineffective and gave my wrist a cramp! The pin vise trick made a world of difference. Unchuck from the drill. Trim any mangled wire ends evenly flush with the hobby knife and the leads are ready to insert.

4. Position the mast holding third arm tool about horizontally and gingerly feed the twisted leads into the mast cutout. Feed gently a quarter inch or less at a time to avoid kinks. Tweezers are helpful if feeding thru/near a ladder cage. Eventually the end will emerge from the bottom of the mast tube, and you can gently (notice the trend here?) pull the leads through with one hand and feeding them smoothly in the cutout simultaneously. Unclamp the LED from the third hand arm. With about a 1/4” of slack before the LED assembly reaches the cutout, grasp the LED assembly with fine pointed tweezers, and insert SIDEWAYS into the signal head with the leads to the rear. The leads will somewhat prevent the LED from going in smoothly, gently adjust as necessary until the LED is fully seated, with the back of the LED fully inside the head. Gently pull almost all slack out of the bottom of the tube to achieve a clean look.

For twin headed signals, insert one lead set until it protrudes from the tube, then start to insert the second set in its cutout. Gently feed it in until it protrudes then finish as detailed above. Using the first lead set to pull the second through doesn't work, but there's sufficient space in the mast tube to freely insert/feed the second lead set.

5. Using a toothpick or other very small tipped instrument, apply a tiny drop of canopy glue to the back of the signal head. The LED tends to wiggle out during this, so carefully reseat it as necessary. Reapply canopy glue as needed after drying to fully enclose the back. When dried, paint the desired color to block all stray light.
For my application, the 14" lead length is perfect. My model railroad is built on a hollow core door topped with 1/2" plywood, then two sheets of 2" foam for scenery base. My scenery is rugged below and above track level, so the extra height was a design intent. The 14" leads are vital for my application for that reason. The extra length allowed me to avoid adding extensions to the microfine leads before feeding them thru the scenery. I was able to feed the leads thru the scenery effortlessly. I had a few packs of 3/32" Evergreen products styrene tube on hand from another project, and its inside diameter was a great fit for the mast tube material.

6: Final installation! I drilled 1/8” holes at the desired install location thru the scenery and base until holed-through. I used a 12” long drill bit I picked up at a hardware store. I installed the 3/32” styrene tube into the holes, ensured it was straight and shimmed as needed, then applied some adhesive to secure it. I noted 3/32” styrene tube above; it enabled me to smoothly feed the leads thru the layout, in exactly the same way as done thru the mast tube. Allow to dry. When ready to install the signals, feed the leads (still twisted from the insertion step) thru the tube and slide the protruding mast into the styrene tube until it seats on the layout. The tubes serve to keep everything straight. I added a tiny drop of canopy glue where the two tubes met, which will keep them from wiggling. At this point, you can untwist the leads and hook everything up, then enjoy your new signals!

The LED works as expected. The only reason that I lowered the rating on durability is the feed wires are very thin and delicate, because it needs to be fed through the signal mast. I had issues with installing the mast so I broke the wires, and needed a replacement. I highly recommend this product.

Showcase Miniatures produce many excellent products from their “Century Foundary” including their 3-color Searchlight Signals. Central to these excellent kits are the 606 (0.060” x 0.060”) 3-color LEDs that they provide through a special arrangement with Richmond Controls (Richmond, TX). As far as I can tell these are the smallest 3-color LEDs to be found. They are not very expensive for these fine LEDs (about $10.00 each in 2022). The signal heads are just barely large enough to accept the LED package if one is very careful to align them as shown in the instructions. Believe me, they do not fit in the signal head in any other orientation (I have failed that test a time or two).
The LEDs are supplied with a copious length of attachment wire, around 14 inches. The wire is 40 gauge, which is small enough to easily fit down the 1/32 inch central tube. Again, careful attention to the instructions is essential. The original signal heads, diecast pewter I think, sometimes present a substantial challenge to prevent shorting out one or more of the LEDs. Recently, Showcase have changed to nonconducting polymer signal heads, which eliminates that problem. Yay for that, and thank you.
Handle the LEDs with the greatest of caution and gentility. If one or more of the signal wires is dislodged it causes extreme problems. The 40 gauge wire is fragile and easily dislodged. You can attempt a repair, of course; but, unless you happen to have a dissecting microscope it is a matter of the greatest care and ample good luck. I have found it essential to attach the wires to an external array of solid copper wire posts so that each time a step is made a functional check can be made. It is only necessary to keep them connected until they are to be inserted in the signal shaft. Due to my own native clumsiness, I am never able to breathe easily until the back cover is glued onto the signal head. I always use RC-56 (i.e. Canopy Glue) for the signal heads in case they need to be repaired or the LEDs replaced.
The signal kits as supplied are exceptionally elegant and prototypically dimensioned with great care. They look like a million bucks when finished. As supplied the signals are very well suited to stationary placement on a fixed layout for a base.
For use on NTrak modules, however, the situation can be quite different. My modules are designed to be reduced to simple flat planes for transport. Consequently, I have to remove the signals between setups and for track cleaning. I mount them on 8-pin DIP headers plugged into sockets on the underside of the modules. The original 1/32 inch shaft is a bit too fragile to be used for repetitive plugging and unplugging. I replace the 1/32 inch shaft with a 3/64 inch brass tube (K & S Metals). Likewise, the elegant stainless steel ladder is replaced with a brass one rescued from a Gold Medal Models “Safety Ladder Kit” (Cat. No. 160-38). These are oversized for the signal, but they are brass and can be soldered to. I use 0.012” brass wire for the ladder braces and solder them to a ½ inch brass plate (1/16 thick) for a base using a small piece of brass angle. The result is robust enough to survive many insertions and removals. Connecting the signal head to the shaft also requires some attention in my experience. The bracket arms supplied in the kit depend entirely on the integrity of the ACC joint between the two on semi-spherical ball. This is OK for a static display, but not strong enough for module use, in my opinion. Consequently, because of a paroxsism of enthusiasm back the 1990s I have a large number of leftover Sunrise Enterprises solid head signals (not designed for LEDs). These bracket arms are larger in diameter than the showcase arms and in addition have a 0.020” “pip” on the end that can be inserted into a like hole drilled into the bottom of the signal head before mounting the LED. Alternately, a small length of 0.020” brass wire can be inserted through two such holes from the signal head and into the mounting arm. This requires some care, in my limited experience.
Well, good luck, of course. Happy signaling.

great tri-color led - looks good BUT it will not fit into the 514 signal head facing the front of the head to get the most light output - have had to change my signal plans from three colors to two which is disappointing but for the station exit signals is acceptable - have to go to "0603" size red/green led to fit into the 514 signal head
SHOWCASE REPLIES: The Tri-Color 606 size LED was never intended to fit into the N scale signal head facing front. Clearly, the instructions have it going in sideways. With no compromise to scale, the light output is exceptional and depends on what resisters you use in the line. We find that this LED is the best on the market and works just as it is intended with very bright full light. See a few of the photos for this listing showing an N scale signal head with LED installed as instructed and working as intended.

Nice LED for HO scale signal heads. When I received mine, there was an issue with the instructions that I discussed with the Mfgr. and the instructions were rewritten to make then absolutely clear. With the changes in instructions. the LED works like a charm and has good colors for signals...

Color appropriate and intensely bright.  Should work for your application.

If you're looking for an outstanding tri-color SMD LED or otherwise, check out the Tri-Color LED (606 size), available from Showcase Miniatures, it is fantastic.

This a great LED. With the continuing advancement of technology, these LEDs are a blessing to the model railroading hobby. It is amazing how this small package contains 3 colors.

Unbelievable how small this product is. To be able to mount the wires on the pc board is incredible! And it works! Leds are bright. Only thing I had issues with was dealing with how small the gage of the wires. Seemed impossible to solder to anything, even to themselves. Other than that, a very good product.

The detail, and scale dimensions are excellent, however, the resistor value on the 3 way light is WAY to high. I had to reduce it to 1k for the green light to work. Once reduced the block signal was accurate and worked perfectly. This is in reference to using the two light system.