Fernco 4" Flexible Cap Part No. QC-104 Reusable caps for pipe ends, testing & cleanouts. Qwik Caps offer a quick, easy way to cap pipe ends, cleanouts and open test pipes. Made of flexible PVC, they're suitable for above- ground or underground use, on cast iron, steel, copper or plastic piping. * Fast, easy installation. * Permanent or temporary cap. * Underground or above-ground. * Low cost and reusable