It's designed to fit a triple chainset, with the outer ring removed and replaced with the thick polycarbonate bashguard, not a twin-ring chainset with a chamfered outer spider face.
While set-up of the single-piece ISCG-05 boomerang is theoretically simple, chainring bolt clearance issues meant we had to remove the washers from the mounting bolts on our SRAM cranks/Giant Trance combo. We also had to find a full set of long chainring bolts in order to mount the bashguard.
Once it was finally fitted though, performance was really good. The broad, shallow angled lower slider guide works really well with a clutch rear mech to keep the chain secure without obvious pedalling drag or noise.
The bashguard is much tougher than previous, thinner Gamut offerings and has stood up to rock and log impacts without complaint. Because there's no roller or other moving parts to jam or come loose, it's been a fit-and-forget installation so far. At 137g, it's light, and it's reasonably well priced too.