I can understand why the Tri-tronics Classic 70 is a favorite among dog trainers.  It has several features that makes dog training a delight to any dog trainer. The Tri-tronics Classic 70 comes in two models, one that is meant for training just one dog, and the other, the Tri-tronics Classic 70 G2 EXP is meant for training several or multiple dogs all at the same time. The new model, which is meant for multiple dogs, is even smaller than the old model, making it more handy for dog trainers. Of course, when you are training dogs, particularly when there are multiple dogs to look after, you want to be as focused to the dogs as possible, and not worry about carrying and operating your transmitter. On top of this, the Tri-tronics Classic 70 G2 EXP collar that comes with the pack is even water-proof, 100%. This is particularly when you are training your dog/s to do tricks that involve water, right?