i am trying to change forks on my Giant Reign and am having difficulty in unscrewing the crown which sits on top of the stem.

it is an FAS headset with a Giant cap above the stem and speaking to my lbs they tell me it is a 4mm allen key fitting. However, when i try to unscrew with the 4mm there is too much movement and it looks like it would round off the hole. If i try to use a 5mm it is too big.

Does anyone know if there is a 4.5mm allen key or has any other solutions?

4.5mm allen keys do exist, as do imperial sized ones. Most likely the first one, although most are 5mm

Perhaps you’ve rounded out the 5mm hole with your 4mm tool? Can you do that?

I wouldn’t think it’s anything other than 5mm to be honest.

Which year and model?

I just took the fork off a 2008 Reign 1 and there were no odd-shaped bolts involved, if that helps.

Are you sure it’s not a torq?

it is a 2007 Reign 0.

i have definitely not rounded it out with the 4mm. The 5mm would be impossible to get in there. The stem bolts and all other fixings are the standard 5mm.

I will try a torq fitting to see if it works and if not then look at getting a 4.5mm allen key