This should be of some help to you. The first photo shows one of the 402 LEDs compared to the tip of a pencil and CM 25's smokebox door. Next photo shows CM 25 with LED and headlight lens installed, with LED lit. The other two show my PFM Berkshire with the LED and lens with the LED lit as well. As for how to mount them, on the engines I've done so far I've tried silicone and liquid electric tape. Both work quite well, but have their own pros and cons. The silicone is easy to use, holds well and has no to little odor. But, it takes awhile to cure, and has to be painted to prevent light bleed through. The liquid electric tape is also easy to use, cures quick and strong, and doesn't have light bleed through. The bad part is it's very stinky.
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