When you see a beautiful face like this one (or better yet, adopt him into your family!) the last thing you want to do is cover it with a muzzle. There are good times and bad times to muzzle a dog, and good and bad muzzle designs. Here are some great pointers on dog muzzles.
When to muzzle? When NOT to muzzle?
Certain breeds, typically greyhounds, whippets and galgos, have very thin skin, thin coats and almost no body fat which means that they are prone to being easily injured during a vigorous-but-innocent game of Bitey Face. It's absolutely natural for dogs to play this game, and it's not as vicious as it looks or sounds. However, accidents do happen. Like my mom always told me growing up, "It's all fun and games until someone gets an eye put out!" Your hound isn't likely to lose an eye while playing, but he can get lacerated skin. Ouchies! So it's a good idea to have all participants wearing a basket muzzle.
If your dog is prone to being aggressive with people, other dogs or animals, then of course you should muzzle him. (Along with getting some behavior modification from reputable positive-reinforcement-based trainers or animal behaviorists!)
If your dog is usually fine but tend to do the "MOOOOM, he's touching me!" tantrums when in the car with other dogs, then it's a good idea to muzzle everybody in the car. Confined spaces often bring out the worst in all of us. Don't let bickering turn into a bloody fight.
If your dog drives you batty with constant barking, that is not a good reason to muzzle him. Go for anti-bark training instead. Which leads us into types of muzzle....
Typically the muzzles used to stop barking are the cloth, leather or tight mesh kind that holds the dog's mouth closed. These muzzles are highly risky and should never be on a dog for more than a few minutes. They prevent the dog from panting which leads to overheating. The dog can't drink with it on - more overheating. Also just from an empathetic perspective, if I was the dog I would feel extremely frustrated with this on my face! In my opinion this kind of muzzle is just a punishment device if anybody other than a trained veterinarian uses it. There are much better options for dog owners. Even if they have cute designs like the one on the left, don't fall for it!
Basket muzzles are a better option. The best designs are roomy enough to allow the dog to pant normally, drink water through the muzzle and even accept treats, which helps with training. Their job is to simply keep the teeth where they belong, and to do it with as little discomfort to the dog as possible. The best materials are wire, plastic-coated wire, biothane, hard plastic and leather.
Bite prevention is a challenge. Some materials like wire, biothane and leather are great for bite prevention... unless the space between the wires in a wire muzzle are too far apart, then the teeth of a very angry dog can actually go through it and puncture what he bites. The best strategy for bite prevention is to really understand your dog's triggers and work with him to avoid those and supervising carefully when you muzzle him.
Sometimes basket muzzles are needed to prevent the dog from eating stuff off the ground, or from simple nipping during dog sports. These muzzles should still allow the dog to pant freely and drink water through the muzzle. These are the styles that we have expertise in.
For snacking prevention in greyhound/doberman/standard poodle sized dogs, we offer 
For snacking prevention in whippet-sized breeds, we offer 
For dog sports, our Double Padded Greyhound Muzzle shown above is also excellent. For whippet-sized dogs, we offer 
If you'd like help choosing a muzzle that we don't offer, or measuring for challenging head shapes like bully breeds, this is an excellent resource: Muzzle Training and Tips Website