For more precision in shooting with these `01 inner barrels from Excel. You can select the length of the inner barrel according to your needs. This cost around £35.00 at Airsoft World... "A tight bore barrel noticeably increases the accuracy of your AEG over the stock barrel so you will get tighter shot groups. Since the barrel fits tighter around the BB your compression will also increase which can boost the guns velocity by 10-20 fps.

Please note: 6.01mm is marginally larger in diameter to your average BB. Please make sure you use very high quality BB ammunition or you are begging for blockages and possible damage to your gearbox."