Stocking stainless steel ANSI Class 3000 (3,000 lbs pressure rating) O’lets are available from The Metal Company in both BSP threaded and socket style to suit schedule pipe sizes.
These are used to connect pipe at a 90° angle. After drilling a hole in the pipe, these fittings can straddle the pipe to cover the hole and be welded in place.
A sockolet has a socket into which pipe can be inserted. A threadolet has a female BSP internal thread into which a male BSP external thread can be inserted.