MV lenses?!??!

I asked this question a long time ago and now, I desperately need an answer. What are M.V. lenses? What do they stand for? Do they come in different sizes and colors? Most important of all, where do i get them? ANY (and I mean ANY ) reply would be highly appreciated. Thank you guys!

MV lenses come in clear, red, blue, green, and black in various sizes.
They can be purchased at model RR shops.

http://users.dwx.com/kingkgk/images/mvlens.jpg

You can check out their products here: http://www.walthers.com/exec/page/manuinfo/v516

Just this afternoon, while I the local craft shop, I saw these little bags of small, facetted clear gem-lihe things that can be glued the things, I quess. These gem-thingys have a flat back and are mirrored under the clear plastic gemstone. I was thinking these might makegood light lenses especially for small scale A/C. The smallest gem is about 2mm in diameter.

You can also use sequins for reflectors in lights.

Ahh.. thanks for the responses, guys!

Regarding MV lenses. I've used them a few times, and have several packages on hand, but have noticed that the clear ones turn yellow with age. This may be over a period of a few years. Anybody else had this experience? I asked the local railroad model shop guy about it, he said yeah, they do yellow. Don't know if this applies to other similar products.