Pet Safe Comfort Fit Bark Control Collar features 6 levels of self-adjusting correction. The collar automatically adjusts the level of Static Correction to your dog's temperament. The patented Perfect Bark Technology ensures that only a combination of both sound and vibration from your dog can activate the collar. A harmless static correction is then emitted to correct the behavior. The QuickFit buckle provides a quick release and a perfect fit every time. Durable, waterproof receiver collar fits neck sizes 8" - 28"; dogs over 8 lbs. Safe and effective for all breeds and sizes of dogs, though it might be too large for those under 8 pounds to wear comfortably. Shipping weight: 3/4 lb.