Depending on what you are sending, a "piece" for Next Day Air can be:
: If a Next Day Air piece is delivered late, you may be eligible for a refund through the UPS Service Guarantee . Package Type Codes - UPS Next Day Air
: Any standard shipping box that meets UPS size and weight requirements (up to 150 lbs). Shipping Guidelines for Next Day Air Depending on what you are sending, a "piece"