I use ziploc containters. The size I use is 11" long x 7" wide x 3" tall. Cut a small hole at the top of the lid about the size or diameter of a golf ball maybe a tad bigger. You don't want the hole too be too big cause you'll lose moisture. I've been using spagnum moss for my all my geckos lay/humid boxes it does the job perfect and never had a problem. I know a lot of other people use cocofiber I never tried it though. Hope this helps