G&G M4 (Combat Machine) Stub for Butstock

I made a stub to cover the area, at the back of my airsoft m4, (g&g riader), to replace the butstock - it is just a simple plug
Inside diameter: 38mm
Square inside Diameter: 13mm
Total length: 34mm
and i added a 2m screw hole 7mm from the inside stop to screw the plug to an existing hole in the stock tube (standard with the raider).
Reason for the odd (2m) size is cause i am using a 4mm screw, screwed in to the plastic itself (no nut thus required).
I printed in using ABS at 100% infill.