Rustoleum Marker Paint Cap

I bought some marker paint to tag where I needed to dig post holes for my deck project. After using 5 squirts of the stuff I realized that the nozzle would be VERY easy to accidentally hit and spray out the florescent orange paint over whatever was in range. I designed this cap to protect it while in storage. It's serviceable and does it's job, but I'm sure someone with better CAD skills can improve the design. It fits quite snugly and can push the other cap that's inside and acc