Muzzle sizing?

Reg has a Baskerville size 4 which is supposed to be for a Westie or similar.
I feel it's too small, I'm pretty sure he would not be able to pant in it and I certainly can't feed him treats...the gaps are far too tiny.
I've been having a look at the Ultra muzzle but, again, I am unsure with the sizing.
Size 1 is for Border/Westie sized dog (which he is) it states that the ultra is comparable to a size 2 or 3 original Baskerville...therefore it would be sensible to go for a size 2?
However size 2 is listed as being suitable for a Cocker or Beagle, Reg is much smaller than those two breeds...I'm a bit lost, but I'm thinking as longs as the head strap fits it's better to have more mouth space?
Help!

Why not go to PAH to try one one?

If it helps my dogs had size 7 and 9 in the old style

They have sizes 4 and 5 in the new one (I always keep muzzles in case of injury etc)

Thanks, I think that will be the best bet.
Although they're far cheaper online.

Try it on in the shop....
....then buy it online

Hee hee, yeah, but I'm such a wimp I'd feel bad

I agree, try them on. I would think a size 2 in the ultra would fit a border or westie. I use size 1 for Shih Tzus.

Thanks, I'll got to PAH but I'm thinking size 2...just tried the size 4 Baskerville on Maggie (also Westie sized) and it fits her much better than Reg, it appears he has a much longer muzzle than her.