This is the original Hop rubber from the M4 NGRS Series.
Tokyo Marui - Original Part Number - NGM4-14
Manual's can be found in the Info Section to see parts break downs, you can also use the Interactive Parts Diagrams.
Or
Link to Interactive Parts Diagram.
Because all brands have different dimensions we can only confirm this to be a 100% fit for the Tokyo Marui Guns listed below unless specifically stated otherwise.
Confirmed To Fit -
Tokyo Marui - HK416C Custom Next Generation Recoil Shock Series
Tokyo Marui - HK416D Next Generation Recoil Shock Series
Tokyo Marui - HK416 Devgru Custom Next Generation Recoil Shock Series
Tokyo Marui - M4 Sopmod Next Generation Recoil Shock Series
Tokyo Marui - M4A1 Socom Next Generation Recoil Shock Series
Tokyo Marui - M4 CQB-R (Black) Next Generation Recoil Shock Series
Tokyo Marui - M4 CQB-R (FDE) Next Generation Recoil Shock Series
Tokyo Marui - M4 RECCE Rifle (Black) Next Generation Recoil Shock Series
Tokyo Marui - M4 RECCE Rifle (Tan) Next Generation Recoil Shock Series
Tokyo Marui - SCAR L (Black) Next Generation Recoil Shock Series
Tokyo Marui - SCAR L (FDE) Next Generation Recoil Shock Series
Tokyo Marui - SCAR L CQC (Black) Next Generation Recoil Shock Series
Tokyo Marui - SCAR L CQC (FDE) Next Generation Recoil Shock Series
Tokyo Marui - SCAR H (Black) Next Generation Recoil Shock Series
Tokyo Marui - SCAR H (FDE) Next Generation Recoil Shock Series
Tokyo Marui - HK417 Early Variant Next Generation Recoil Shock Series
Tokyo Marui - AKS74U Next Generation Recoil Shock Series
Tokyo Marui - AK102 Next Generation Recoil Shock Series
Tokyo Marui - AKS74N Next Generation Recoil Shock Series
Tokyo Marui - AK74MN Rifle Next Generation Recoil Shock Series (Discontinued Model)
Tokyo Marui - G36K Next Generation Recoil Shock Series
Tokyo Marui - G36C Custom Next Generation Recoil Shock Series