These are leads for running rigging. If it is fairleads for mooring line you need, try here
Handsome is as handsome does
Wykeham-Martin furling gear looks like - indeed is - a relic from the 19th century. But it works. here
Traditional ash or galvanised steel. The dimension quoted is the inner diameter, so you need 1 or 2 inches clearance.
You can specify a horse (or traveler in US English) link.
Useful not only for mainmast track, but also for clew outhauls, and hatch slides