This is the Black Dog 'Sonic X' 15 round short profile magazine for AR15 .22 conversions.Manufactured from tough polycarbonate sonically welded together, instead of the hex screws and brass inserts found on the previous X form model.The full length weld makes them more durable with repeated impacts on concrete range floors, they are also cheaper and lighter without the screws and assembly.Available with either Black Nylon or Stainless Steel feed lips, both of which have a single mono block shape, so no risk of seam splits or chips. Both types are extremely hard wearing, so material choice is down to personal preference, tough slippy black nylon or shiny and durable cast stainless steel.Compatible with all AR 15 .22s using the common CMMG/Ciener/Atchinson format mechanism, including: Atchison / Ciener conversions Bushmaster C22 CMMG Chiappa DPMS JP rifles Kriss Defiance (works with the Nylon Lip type) Lantac Sig Sauer 522 (the branded 522 mags were an early Black Dog design - we recommend the Nylon Lip model for 522s) Spikes Tactical Tactical Solutions Target Master