Carbonation Cap Wrench

Recently I started carbonating my own beverages. Rather buy a SodaStream or some other commercial offering, I simply bought a five pound tank of CO2, a regulator, and a Stainless Steel Carbonation Cap sized for standard two-liter soda bottles.

It works well, except it's sometimes difficult to screw the cap on tightly enough. The cap has flats for a wrench, but I don't usually have one handy, and I don't really need that much torque, so I printed up this.