Strike Industries products are designed by shooting experts for the shooting sportsman.The Strike Industries Flat Wire Carbine Spring is an inexpensive and easy upgrade for your AR-15. Designed to smooth recoil, this spring produces an increased bolt load yet requires less compression force improving reliability in cycling.SI Flat Wire Springs are made from cryogenically stress relieved 17-7 PH steel to provide greater consistency, longer spring life, and increased resilience to high cyclic rates.Features: Cryo-cycled 17-7 PH steel Decreased harmonics lessens system vibration for faster follow up shots. Increased bolt load Reduces distracting AR twang Outside diameter: 0.94" Inside diameter: 0.75" Length: 13 7/8" Gauge (Flat Wire Profile): 0.045" x 0.0935" NOTE: Limit 2 per household. Quantities exceeding 2 will not allow checkout. We are fully staffed and processing orders. Standard orders are shipping in approximately 1 business days or less. FFL orders take approximately 5 business days or less if you can provide us an actively receiving FFL location.