I have purchased a total of five Innotek Smart Dog Extra/Replacement Collar Receiver's, I have bought them from Petco as well as E-Bay, they are very durable and designed to work with these systems SD-2000, SD-2050, HF-25w, HF-200w, HF-201, CKF-25w, CKF-200w. I have the Innotek Basic In Ground Pet Fencing System SD-2000 and they work great with it. I have had now problems so far. The battery needs to be replaced every four to six months depending on how often your dog tests the system. I have some that will test to see if it is working everyday and some you can't drag near the wire. The collar is nylon and if you don't cut off the end and burn it after fitting it to your dog they will chew the excess and it will start to unravel, I would also like to see Innotek put a low battery led light on the receiver box so I wouldn't have to check batteries every month.
Pros: Durable, water resistant, works with more than one system
Cons: Nylon collar can be chewed and made to unravel, cost of replacement battery's, no low battery warning light