I love these things, whilst i personally don't have this product in black (i have a white one) they work really well in keeping nasty stuff off your suspension stanchions and headset as well as reducing spray in your face. Technical stuff aside i think adding one of these to your bike just makes it look so much cooler.
This mudguard might protect lower end of head tube, but it won't in my experience even come close to protecting your legs from road water. To be effective against wheel spray a front mudguard needs to intercept the water much further back, ideally after less than 90 degrees of wheel rotation from point of road contact. This tiny clip-on mudguard might be useful specifically for preventing accumulation of mud on front non-disc brakes on MTB. For general commuter applications, try a front mudguard that reaches back much further.
Thank you for your comments regarding this MTB mudguard. You are totally correct in saying that this only prevents mud from contaminating the headtube of the bike which is it's intended purpose. For commuting you will need a different product which covers the whole rear quarter of the front wheel.
Peter Lazarus, National Cycling Manager, DECATHLON