Nichols Model 10-B Therm-O-Vac uses styrene plastic sheets that measure 14” x 20” (280 sq. in.) x .020" to .060" thick.

Video (starting at 1 minute): https://www.youtube.com/watch?v=74l7hfbgi0s&t=1m6s

Website: http://www.iasco-tesco.com/

http://www.iasco-tesco.com/index.php?page=shop.product_details&flypage=flypage.tpl&product_id=240&category_id=14&option=com_virtuemart&Itemid=2

Preferred plastics:
- PETG
- HIPS (high-impact polystyrene)
- Polyethylene Sheet - LDPE (advanced users only, for small parts)