Air Arms S510 Extra .25 breech seal?

[DeanB]

Anyone have a S510 Extra in .25 and know what size the breech seal is and possibly where to order one in the U.S. , not wanting a whole reseal kit.
Can possibly get one at hardware if size is known.
Thanks.

 

[DeanB]

Found some at Pyramyd Air but would still like to know exact size if anyone knows.

 

[BSJ]

Contradictory information here. https://www.airarmsspares.com/air-arms-spares/ Search for FP122.

I think 6mm would be too small for .25 cal.

Most likely, 7mm ID x 1.5mm Cross-section, NBR 70.