O-Ring For Benjamin 300-DIN Male Adapter, Fill Adapter

If it is a standard Din 300 112 o'ring. My Joe B. DIN 300 takes the 112. Small usually are 111 o'ring. Regular cheap black buna 70 or 90 duarameter work also. The polyurethane are just more durable. I bought some just for future replacement.
https://www.amazon.com/gp/product/B017WOD5C6/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

https://www.amazon.com/Captain-O-Ring-Polyurethane-Durometer-Translucent/dp/B017Y3QIFG/ref=sr_1_1?s=industrial&ie=UTF8&qid=1505421699&sr=1-1&keywords=captain+o+ring+112

*EDIT http://www.captainoring.com/uploads/4/0/8/9/40890501/scubachart.pdf

Thanks Dirte. Your post helped me too. My 300 DIN came with an undersized o-ring. Captain O-Ring supplied me with dimensions within a couple of hours of emailing them a request which helped me to confirm that I was given the wrong o-ring and the #112 was the correct one. Ordered mine from the manufacturer rather than the corporation that thinks it has the right to control my access to information.