What kind of blocks are these?

[dewent]

I want to add an additional block to the base of my mast.

As you can see there are spare vertical pins available.

Can anyone help - what am I search for? What are these blocks called?

Thanks................

View attachment IMG_0827.jpg

 

[Minerva]

Harken 57mm ESP Mastcollar Block

 

[dewent]

Thanks for the info.

 

[AngusMcDoon]

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