This little block is used for the "dingleberrys" (the 2 turning blocks on the mast for the outhaul) and can also be used at the clew of the sail either on a clew hook or a shackle.
These are the same Harken blocks that come with the boat when new.
These fit the Maffioli Swiftcord we have on our Line page.
Sheave dia. (in) 7/8
Length (in) 1-1/2
Weight (oz) 1/2
Max. line dia. (in) 1/4
SWL (lb) 200
Breaking strength (lb) 1200