There are a wide variety of collars, harnesses and training methods on the market. It can be quite daunting as you want to make sure you get the right one.
If your having problems with your dog pulling on the lead then this is an item that I would recommend to use. The harness comes in small, medium, large and extra large. It does not restrict the dogs natural movement unless you pull on the lead to stop them. It's a great training method and I found there was a noticeable difference after only 1 week. Once you have stopped the dog from pulling you can also take the harness off and just use the collar, so great value for money.
There is one problem I found with the harness, when using it to train my long haired german shepherd his fur wound get caught resulting in a sore area under his front legs. Unfortunately due to this I stoped using it after around 1 month. I would say it was better suited to dogs with short hair as it's less likely to catch any hair.
It's not an expensive product for what your getting either:
Extra Large= £7.99
You may even get them cheaper if you shop around so all in all a great item.
I have a boxer and we'd tried absolutely everything to try and get him not to pull but nothing had worked. Until I found the Walkrite Training Harness. Instantly I could walk my dog after 2 years of trying!