Looking at the sizing details for the S – its says 'Top opening – 15"'. Now my thigh above knee is 15" diameter so is that the right size or is it going be too big and just slide down my leg?

They've got velcro straps top and bottom. I'll measure mine and get back to you in the morning.

Cheers.

My thigh diameter is 15" too and I've got the mediums. Where they adjust on my calf is 13". The diameter round my kneecap is about 15" too – knobbly knees. The smalls would definitely be too small for me I reckon. There's quite a lot of adjustment too. The 15" opening is unadjusted size by measuring mine.

I'm not sure I'd trust the sizing chart too much. My bro bought me some Race Face Rally's but they were way too big in the end. I tried the Straits in store.

Hope this helps mate.

That's awesome – many thanks for taking the time. Happy new year!