Maxim Defense MXM47572 JP Silent Captured Spring System for AR platforms. JP Silent Captured Spring (SCS) designed for Maxim Defense CQB Stock System to pass a guide rod through an open channel in the bolt carrier group during fire. Material: Tungsten/Stainless Steel. Finish: Tungsten. Model: JP. Type: Silent Captured Spring (Capture Spring). Not available to ship to California, Illinois, or Washington. UPC 680017475727. Mfg Part MXM47572; SKU ACC-MXDEF-MXM47572.