Cz 634 owners this is the breech seal size...

[rwsmike]

And if you need the piston seal or spring vortex has the proper size .

 

[laalex]

Thanks for the heads up. Thinking of tuning mine when I get the time.

 

[Houli]

Thanks Mike, I took note.

Also reminded me to get it out of the safe for my next shooting session!

Cheers