The MPA Adjustable Mag Catch is designed to replace your standard mag catch when your magazine isn’t feeding properly. The adjustable catch utilizes a 1/16″ hex key so the user can fine tune the magazine height. Compatible with any MPA BA, Comp, ESR, Hybrid, BA Lite, CSR or Ultralite Chassis. Using a 1/8″ punch, remove the dowel that holds your standard magazine catch in place, and substitute the adjustable catch. The MPA Adjustable Mag Catch does not include a dowel and compression spring, as you should already have one of each from your standard mag catch.