The M8x1.25 threaded cap to prevent oil spillage from the disconnected pipe and dirt penetration inside it. Just screw it on with hand. Made of ABS will seal the cut. You can use a small peace of rubber/silicone inserted in the hole to seal pipe cut better.
0.15mm. 0.20 tested well too both with 0.3 nozzle
Print it open hole to top.
No post processing. May be little bit tight in threaded part on first usage.