​The precision molded MEC Hop Up Rubber has a slightly narrower inner diameter at the entrance and extra coverage for the top of the barrel open cut area for vastly improved air sealing. Internally, it provides two equal pressure point of contacts with the bb resulting more effective range and more stable accuracy. The MEC GBB Hop Up Rubbers are compatible with Tokyo Marui MWS AR-15 Series, Tokyo Marui Hi-Capa 4.3/5.1, Tokyo Marui 1911 series and VFC made Elite Force/Umarex Glock Series and Sig Air P320-M17/M18. The MEC AEG Hop Up Rubbers are compatible with most AEG airsoft in the market Two (2) hop up rubbers are included.