Another hop-up adjustment tool for the WE Airsoft M4 Gas Blowback Rifle is available and you can find it right now at Airsoft Atlanta... "The ASP WE-Tech M4 GBB Hopup Adjustment Tool is a neat flexible hex driver that easily fits inside your WE M4 gas rifle. No more awkward adjustments with an allen tool! To use, simple pull back your charging handle and insert 'stiffy knob' into your chamber area, and adjust your hopup. Very easy!