Cherokee 35 Model Main Spring is multi-processed for long operational life, ground and polished ends, proprietary tempering process using the highest material grade. During final tempering they are coated with a specially formulated hard but fexible finish. This is a high tech derivative of PTFE and Teflon and its self-lubricating multislip properties eliminates the need for conventional spring lubrication. Maximum power is maintained for longer than most other springs.  High Quality Air Rifle Spring for Optimum Accuracy & Power  Made in India from Finest Steel  Striking Power Pre-Tested at Full Compression for High Impact & Elasticity  Best fit for National, SDB, GI, UTA, Classic & other Standard Air Rifles 37 Coils approx SPRING DIMENSIONS: Dimensions in Millimeter (Approx) “A” Spring Outer Diameter : 21mm “B” Spring Innner Diameter : 16mm “C” Spring End-End Length : 317mm “D” Pitch of the Spring : 12.5mm Spring Wire Diameter : 3mm