Pelican 0340 cube Case w/Foam (Black) Pelican cases are kept watertight through the use of a tongue and groove fit and a polymer o-ring. Pelican cases come standard with an Automatic Pressure Equalization Valve which releases built up air pressure while keeping water out. Pelican's Pick N'Pluck foam lets you customize the interior. Stainless steel reinforced padlock protectors Pre-installed wheel plates with removable castors