Outwardly these fenders look similar to SKS's, sharing a similar material for the guard (ABS plastic) which is just as tough in our twist test. They do have an advantage over the SKS in being highly adjustable, the stays having independent sliding mounts allowing plenty of fore and aft rotation of the guard.
This does make fitting them trickier than a fixed guard but with patience it allows you to get the fit just so. The stays don't have a release system but we found that if an object was trapped between guard and tyre, the independent stay mounts allowed the guard more twist than a fixed mount, making for a lot of drag rather than sudden stopping – not ideal but better than nothing.
Although the quoted width is 37mm (for tyres up to 28mm) the profile – more rounded than the square-ish SKS – makes them appear bigger than this, and they're also available in 45 and 60mm widths.
In all they're a great guard especially with the adjustability, marked down for the small hard plastic flaps which have little effect, and the lack of a safety stay feature on the front guard.