United Security Products 240 TwistLoc Series Threaded Metal Contact. .5" gap 1/4x1/2". Priced each, sold in 10 packs1/4” x 1/2” Size – Precision Machined Metals • 100 Million Life Cycle Operation • Lightning Resistant 1.0 Amp Contacts • Closed Circuit • One Turn Locks in Place, One Turn Removes for Tests