I'm on a new forum and there is some discussion going on about prong collar fitting. As usual, people are being sent to the leerburg site, but I really don't like that article all that much because in my opinion the collar being used is too big for the dog and it still sits pretty low on the dog's neck. Dobermans have giraffe necks, and it should still be up under the ears.
So, here are Riggs and Connor modeling their collars.
Connor works on a size small - there are 12 links in his collar.
Riggs works on a micro - 18 links in his collar
The collars fit right up under their chins, and the leash ring belongs at the top of their neck behind their ears. This keeps the prongs at the most sensitive part of their neck - where you can give the most efficient correction possible. You should not have to yank on the collar, a finger twitch should get a response from your dog. I had a 110 pound woman handle her 130 pound dog aggressive Great Dane on a medium prong in my class with no problem, as long as it's where it belongs.
If your dog is under 75 pounds, get a size small collar and just get extra links for it. Smaller links and more of them make for better, more efficient corrections, which means that you'll have to give fewer of them! I've had a Mastiff and a Great Dane in my classes, I have yet to have a dog need anything bigger than a size medium collar. When I want a backup collar for safety, I used a nylon slip lead. I highly recommend using a backup collar at all times, you can never be too safe. Using a flat collar as a backup collar will interfere with your prong collar unless you are using two leashes or have a coupler.
In my opinion Herm Sprenger is the best brand. They have rounded prongs, which are better for corrections. They also have a small plate at the end for putting the collar on. I never use rubber tips on the collar, blunting the corrections defeats the purpose of the collar... don't use it in the first place if you don't want to give your dog corrections. You will just create conflict, if your dog needs a light correction, give it a light correction. If you can't give it a light enough correction without rubber tips on the collar, then it doesn't need a prong collar.
A note about micro prongs - Riggs competes in weight pull and has pulled a ton in training. Yes, a ton. He is plenty strong. He could straighten those links out, but he is at a point in his obedience training where that is not an issue. I very rarely use a prong on him in training at all, but when I do, that is the one I use. Micros are not appropriate for dogs that are above "toy" unless they are into advanced obedience. They are not very strong, but at the same time, they are capable of giving quite harsh corrections.