This upgrade one-way fill nipple fits the fill adapters of most PCP airguns including Crosman & Benjamin models. It's made of stainless steel, extremely well machined and extremely reliable. The threads are standard 1/8 NPT tapered. The pin closes-off the opening to keep particles out between fills. After extensive problems with various fill nipples over the years we've had excellent results with this new design. They're the only ones we use for our custom airguns and fill adapters now. This is a full-sized fill nipple, it's intended for fill adapters and fill equipment with deeper or looser-fitting sockets, it often fits too tight or is too long for shallow-sockets like those on tank regulators.