Supco sfl51610 5/16 refrigerant safety locking caps, package of 10 maintain compliance with local building codes with these durable, value-conscious safety caps. Lightweight, uv resistant thermoplastic composition. features/ benefits compatible with r12, r22, r134a, r404a, r410a and other refrigerants. no tools required- simply tighten by hand. resistant to fat, grease, oils, and solvents..