This is a DIY 7 segment display, with a 3d printed housing. The print is 1 layer thick where the light shines through, which makes the segments almost invisibly when not on. The disply is still plenty bright though. Use led string lights which fit perfectly in the holes in this model. I used the 3528 red leds. Watch this video for details about making this:

https://www.youtube.com/watch?v=OxdHaD6YI0A