Actually I drilled for the fuel hardware in the clear childproof part located inside the white cap. (mine was clear) I removed it with a small screw driver. the top part of the white cape doesn’t have the threads. When I’m finished flying, I just remove the fuel line that goes into the bottle, pop the red cap in to seal it and screw the clear cap on. My friend does almost the same, but he removes the clear cap with the fuel hardware and fuel lines altogether, places the red cap in and then uses a spare white cap on top. Ether way works great.