This tire pressure monitoring system was defective. One of the caps did not register and leaked air out if the tire. Another registered pressure even when removed from the tire. I returned the defective purchase per seller's instructions and provided my PayPal account at the seller's request for the seller to refund the postage. I received the refund for the item through ebay, but have not received a refund for the postage despite providing the receipt as requested and making multiple requests.