"Cheap and cheerful. It works but I doubt it will last for long. The price is reflective of the product. Quick tip: don't use the brass plated plate as you will need to dig deeper into your frame to make it sit flush."
"Installed four over two years now all broken. Plastic wheel is not nylon so no real strength. Alternatives with brass wheel, better axle, and very similar dimensions only 25p more. Search for Sash Pulley.
For all the difference Screwfix should change to a better source."