These Lumenok CAP nocks are the nocks that we manufactured for use in Parker Crossbows, and were previously sold by Parker. They are made to fit bolts that are .300" on the ID. Nocks weigh 28 grains. Gold Tip bolts .300" ID Lumen-Arrow bolts Black Eagle bolts Bloodsport Bolts Victory bolts Element Bolts Parker Red Hot Bolts ( by Gold Tip) Each has a replaceable battery (Lumenok RBS)