I bought this because I was unimpressed with what I regarded as the extortionate cost of Canon's own hood and while I don't mind paying Canon prices for optics and mechanicals, I figured that a lens hood was pretty straightforward and less demanding of engineeering quality.
The hood itself looks fine and fits the lens very tightly. The only problem is that it looks as though it was designed to fit in the reversed position, with the petals facing rearwards. In this position the petals are orientated correctly, with the longer ones at top and bottom. When you fit it for use, the longer petals are at the sides, which results in serious vignetting at focal lengths shorter than around 24mm, although at longer lengths than this, the problem disappears.
If I find this to be a problem (not had much cause to worry about the sun yet, as it's winter here) I'll be looking at whether I can saw off the front and re-attach it at 90 degrees to its current position to fix the issue, although this might render the thing completely inoperable if the bond fails!