This fitting wraps around a 1" diameter tubing and attaches without drilling any holes. It is an easy way to add an eye for a block for a spinnaker sheet, preventer, or additional lifeline wire.
All Catalina sailboats have used 1" diameter tubing as standard equipment. But if there is any question, measure yours before ordering. We have encountered boats where a previous owner installed a stern pulpit or stanchion that was smaller 7/8" diameter tubing.