Hi.. Sorry its taken so long to get back to yer.
The B11-1 " wincheaster copy"
Seal size is....
27mmOD 1"-1/16th
12.7mmID 1/2"
6.4mmThick 1/4"
The seal fits on the piston by way of a tapered button.
Ps...These sizes are from a used seal so may very abit from a new seal.
kiwi
cfx .22
Geox 1.77 underlever
B11-1 X 10
B2 X 4
1088 pistol