"Does what it says it does really. A little tricky to bend and shape to the right angles but with care you can get there. I found the vent cover screw points a little close to the edge of the hole in the wall but I think that would be the same for any vent like this. Also a lot cheaper than any other other DIY chains."
"Use a piece of 100mm plastic pipe through the wall. This will mate with the spigot on the outer cover. Use a 100mm connector to join the plastic to the aluminium. The plastic will fit core drill holes."