Cels Forum

I recently purchaced 5 Escaflowne cels and I was wondering if someone could tell me some information about the plastic envelopes that cels are usually protected by. I  recieved 5 cels from Anime Lane and they arrived in only 3 envelopes. I would like to get 2 more of these envelops. Could you tell me where I could get some or what they are called? Or any info that might lead me in the right direction?

Thanks 
Andy Allman