There are two things to think about when looking at these photos.
1- If the dog jams its snout into something (a human or another dog) will the muzzle be pushed back over the dog's eyes.
2- If the dog hates the muzzle and it lays on its back and uses its feet to push the bottom of the muzzle up and away from the dog's head - ask yourself if you think that muzzle will come off.
Good Fit - Not too short, not too long, 3rd strap between the ears for extra security and enough room to pant
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Too small - Not enough circumference, inhibits dog's ability to pant
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Too Big - Length is a bit long, rests too low on the snout, circumference is way too big
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Too Big - Circumference is way too big, do not need that much pant room.
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To small - Nose is resting on the front of the muzzle.
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Way too big - Circumference is much bigger than needs to be.
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Close to OK but too Big - Length is a bit too long and pant room is too much. Fins (sides) also seem a bit tight.
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Too big - Excessive pant room - circumference doesn't need to be that big.
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While this style of the muzzle is secure - because of multiple straps, we feel it does not need to be as big in circumference.
*Note: Baskerville muzzles are not bite-proof.
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The muzzle is too big. Look at the room under the jaw. If the dog really wanted to get that muzzle off it could do it.
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These examples are not to be used to call out those who have ill-fitting muzzles but rather to give you an idea of what to look for in a proper fit. There are a lot of different muzzle sizes, shapes, and styles, and no 2 dogs are exactly alike, even within the same breed. Finding the perfect muzzle fit is often a process of trial and error.