I've used Knox many times and they are great. Top quality carpet that actually fits.
I've bought one Truefit and seen many. Yet to see one that fits. The last one that was bought into work I honestly think I could have made a better fitting, better quality carpet with $30 worth of Bunnings carpet and a heat gun. It was crap.
Same goes for their sound proofing. Never use that again either.
Knox is a bit dearer, but 5 times the quality of Trufit.