PDI VSR-10 450~520 FPS Spring

etails:This is a high-grade Chrome Silicon Steel PDI VSR-10 Spring. All PDI springs are variable pitch, giving light compression and a fast return.PDI got 520 FPS using a TM VSR original inner Barrel & chamber, PDI Precision cylinder set HD and 0.2g BB's. Your results may vary.Caution:These Springs have a 13mm OD and 11mm ID. They need to be used with 9mm spring guides. They also require a piston with a larger ID, so PDI recommends their VSR-10 pistons for use with this spring. Please make sure your VSR-10 parts are compatible prior to purchasing.