Airsoft M4 AEG Crane Stock Battery Cap

When I first started playing airsoft, my first AEG was a G&P M4 CQB. Unfortunately I lost one of the battery caps from the crane stock before I even knew they were there to lose. Unable to buy the part online, I eventually designed this replacement, which works!

The outer diameter of the cylindrical section is 20mm.
The length of the pear-shape section is 28mm.

I made these in 2014, those parts are easier to buy online in late 2015.