Suitable for smaller yachts only!
I wanted these to stop the halyards banging on the mast.
They work, but they are not designed for medium-large sized yachts - my boat is 15m.
The tension required in the halyards to keep them in the hooks makes the plastic deform and lose it's shape, especially in the heat (the boat is in the Canaries). The halyards then become lose too and we're back to same problem.
I'm also concerned about the durability of the product in UV light, but so far it's OK.
The conclusion is that they work, but probably better suited to boats up to 12-13m and maybe not in areas of high temperatures.
It's a pity you can't buy bigger ones.