A series of e-collar that contains features of a professional training collar at a very affordable price. It uses a standard 3/4" collar straps that also comes smaller receiver collar designed for smaller dogs. It has an easy-to-use, ergonomic transmitter that uses low to mid-range power system that has a 1/2 mile range. The rheostat dial allows gradual increases in stimulation with no jumps between levels (0-100) that can be adjusted depending on the owner's level of training . It also has Nick and Constant stimulation with Non-stimulating vibration (pager) function. Both receiver/collar and transmitter are fully waterproof and uses LED as battery life indicator to know the how much power is left for both transmitter and collar. This unit uses Rechargeable, user-replaceable Ni-MH batteries and great for small to Mild-Mannered Dogs that weigh as 15 lbs.It comes with 2 unit. Dogtra Element 300M is designed to train up to 1 dog while Dogtra Element 302M allows you to train up to 2 dogs.