API specifies only “Type R”, with both oval and octagonal profiles designated.
Some very old flanges that utilize Type R ring gaskets have ring grooves with rounded bottoms, and specifications for these flanges called for the use of oval gaskets in these grooves, but current specifications for API flanges no longer show these rounded bottom grooves.
In actual practice oval gaskets seem to coin easier than octagonal gaskets so we at Weason prefer oval gaskets for make-up and test, otherwise we find no difference.
