CZ 457 Bolt Cap. This part is fully compatible with the original CZ bolt cap and installs exactly the same way. The version shown in the photos was printed in PETG. While I encourage experimenting with other materials, please note that they may not maintain the required tolerances or could be too weak and prone to cracking. 

Before installation, I recommend checking the diameters of the pin hole and the firing pin indicator hole. (In my print, these required slight reaming.) 

To avoid losing the pin or damaging the bolt, the pin should fit as tightly as possible.

Prefer material: PETG

Prefer infill: 100%