Started off with the normal screw on subaru type and had three sets removed by some kind young lad who must have thought that he'd save me time checking the tyre pressures each time I went to the garage. It worked but I did prefer them on , looked so much nicer. So off we go to our local dealer who, now calls me by my first name, and he recommends that I fit the Prodrive caps with the allen , great just wot I'm after, pay the man and set off home to fit them straight away. That will stop them going for a walk about on there own. Take the allen key in doors, so as not to lose it, and goes of to bed happy in the knowledge that my new dust caps will still be on the car in the morning. The young lad who was so kind before, got so upset by my unreasonable behavior that he took it opon himself , Not to prize them off , Not to take the whole wheel including locking nuts , No he takes the whole car, o bless his little Cotton socks. What have I learnt from this, air is free and you don't have to lock it in. Only joking I think the car is still in the garage best just go and have a look.[][][]