Guarder 1st Steel Hop-Up Kit for KSC/KWA MAGPUL M4/LM4 GBB Rifle 
 Steel/ Plastic/ Cooper/ Rubber Construction 
 Hopup Gel made by 70° Silicone Gel 
 Steel Hopup Round 
 For KSC M4A1 & KWA MAGPUL GBB 1st Version 
 
 2nd Version Must Change the inner Barrel, You can Choice Guarder Inner Barrel Series: GUARDER TN-21、TN-22、TN-23、TN-24 
 As always, upgrading AEG require necessary skill & technique to dissemble the gearbox, consult expertise if needed
 
                        
                       
 
               
               
               
               
              