What size Breach O-ring Hatsan Flash and Hatsan AT44 in .177 caliber

[airgun14]

Hi, I would like to know what size in mm the Breach O-rings are in Hatsan Flash and Hatsan AT44 in .177 caliber ?

Part number does not help me, I need to know the actual sizes

THANKS

 

[airgun14]

found it, 4.5x1.5