Plastic?

Ive seen some alternative cages that have, what it looks like, a plastic liner around on the grids? I know its not coro and I was wondering what it was called and were you get it. I am going to save up allowences(sp?) and make my guinea pig at my mothers house Georgie (female) a c & c cage. She is 5 years old and I also plan on eventualy getting her a buddy to make her last years wonderful. I already have 2 other guinea pigs at my fathers house and was trieing to get my mom to let me bring Georgie to my dad's for the rest of her years and make a bigger cage and my mom said that she couldn't give Georgie up because she loves her too much. So I plan on making a C & C cage out of an Old shelving short of unit, grids and that liner.