What is the difference between the 35-6HB, CP 35-6HB, and ULT 35-6HB?

The 35-6HB will accommodate six strips of 6 frames of 35mm un-sleeved negatives and is made from archival 4.8 mil polyethylene. The CP 35-6HB also accommodates six strips of 6  frames of 35mm un-sleeved negatives  but has an additional 812” x 11″ pocket attached to the preserver for a contact sheet. The ULT 35-6HB will accommodate six strips of 5 frames of 35mm negatives but the openings are slightly larger in order to accept a strip of sleeved 35mm negatives. The Ultima negative preservers are also 6 mil polypropylene.