5/8 X 5 shoulder bolt. This bolt doesn’t need any jam nut to close the ring.
with black buna gasket
2″ and 3/4″ Tite Seal lined plugs buff epoxy phenolic L-35 with Black BUNA gasket
2″ and 3/4″ TITE SEAL lined plugs clear phenolic L-1 with EPDM gasket