Creedmoor AR-15 Upper Vise Jaws with Magnets There's now finally an upper receiver jaw set that's easy to use! Just attach the Delrin pieces to the vise jaws with the magnets, hold the receiver in place, and tighten the vise. Made from dishwasher safe Delrin, you don't have to worry about scratching your receiver or it falling out of those other flimsy soft jaws.