End stop or cap for 20mm electrical plastic conduit

I use 20mm plastic conduit pipe for my spool holder. I designed this end cap to fit using a friction fit into the pipe ends. It prevents the spool falling out of the spool holder during use.
The end cap is easily pulled off and and on to allow different spools to be placed onto the pipe.
The pipe internal diameter is not entirely round and I guess it may vary between makes of pipe, so scale as you find necessary.