Film sleeves are available in archivally safe, clear 3 mil Polypropylene or Polyester (Melinex 516, DuPont's replacement for Mylar D)
A self-locking side fold holds film in place; Sleeves "unlock" to open completely for safer film removal without sliding image inside the sleeve
Both materials, polypropylene and polyester, will not interact with film and prevent interaction between adjacent items in long-term storage; Choose Polypropylene for economy, or Polyester ("Mylar D") if the very highest optical clarity is required