The new black bone receiver will deliver vibration/shock truly under your control. The is how it works: if the button is pushed once, the receiver will vibrate or shock once, not three or four times in a row. The intensity of the low level(L1 or L2) is truly mild while the high level(H1,H2) delivers quite a jolt to get your dog"s attention if vibration does not work. This 300 meter range remote control dog training shock collar system has shock and vibration corrections for each dog. This collar has the most intuitive operation and simplest button layout for fast access and instant control of your dog"s unwanted behaviors such as excessive or aggressive barking or or chasing cars or for obedience training. This collar has 3 vibration command buttons:V1 for dog 1, V2 for dog 2 and V for both dogs. This two vibration setting will serve different training purposes. For example,V1,V2 serve as warning before shock and V as attention call for two dogs . This is to make your training easier yet more efficient. This sale includes: 1. One remote control w/9V battery; 2. two water-resistant(not waterproof) rechargeable receiver with adjustable collar straps 15"-23"(36cm-58cm); 3. Wall charger with dual USB charging cable(charge both receivers simultaneously); 4. Metal prongs,Shock test light; 5. Manual; 6. Six-month free replacement warranty from seller.