The Freedom No Pull harness is extremely effective for training and minimizes the effect of pulling. Factors contributing to the success of the harness include the tightening effect of the loop on the harness, the location of the loop and the reconfigurable design that allows you to attach to only the back or to the front and back of the harness simultaneously. When selecting a size please use the exact girth measurement as the primary method of ordering. The weight is ONLY APPROXIMATE and should be used as a guideline not the determining factor. Standard sizes are listed on the website. Custom sizes can be made for dogs larger than the standard 2X size.