1.5' Tri-Clover Rings from McMaster?

[theck]

I see these from McMaster:
http://www.mcmaster.com/#tri-clamp-sanitary-tube-fittings/=vanmot

Which are $2.38 each for the 1.5" but I see some sellers are doing o-rings. Anyone know what size I would need for the o-rings?

Would it be:
http://www.mcmaster.com/#9396k215/=vanpas

 

[Dbaudio]

For the sake of a few dollars I sure wouldn't trade my silicone tri-clamp gaskets for little tiny O Rings

 

[theck]

Kind wondered that too. I'll snag a gasket or two. They are cheap enough on eBay. Thanks.