Prong collars are helpful if your dog is very desensitized to leash pressure. If your dog is at risk of injuring you or itself when pulling hard on the leash, the prong can help mitigate the issue by making leash pressure more acute, allowing them to respond to much subtler pressure on the leash. We generally prefer the 2.25mm for most dogs (you may need extra links if you have a larger dog or consider a larger prong size) and highly recommend adding in a buckle fastener to make getting the collar on and off much easier.