How effective are these electric remote dog training collars. Also I’m finding that there is a very large price difference between the UK available products and the products available direct from Chine. Where would be the best place to purchase it from. I have an 8 month old very lovable but naughty Weimaraner. “Casper”. The kids and I have sought of given him to much of a good thing and now he is getting out of hand Eg when asked to get off the sofa, he likes to show his pearly white teeth.