6" Spiral Torsion Spring, also called a Clock Spring Universal replacement on all externally mounted spring powered tarp systems: US Tarp 11121, Donovan 2416, Roll Rite 47230, Cramaro 224200, Mountain K0199, Buyers 3011876. Not compatible with Aero Easy-Cover Double Torsion Springs Durable and built to last, made of all steel 1/2" wide steel band measures 3-3/4" wide when fully coiled Usually used 4 or 5 on each arm of the tarp system 6" spiral torsion spring, also called a clock spring, is made of steel. 1/2" wide steel band measures 3 3/4" wide when fully coiled.