Hi,
Orings are available most everywhere.I think the nozzle and rail orings are the same.A little lube during installation is a must.If you are using pintle style stockers, be careful of the hats;they break easily.Those are also available.
Hi,
I know that was your original question, sorry but I will have to guesstimate.Approximately7/16 OD with a 9/64 cross section.Instead of sizing them, buy the kit from Felpro, or such.