Mass. Gen. Laws ch. 106, § 2A-509: Lessee's Rights on Improper Delivery; Rightful Rejection

Section 2A–509. (1) Subject to the provisions of Section 2A–510 on default in installment lease contracts, if the goods or the tender or delivery fail in any respect to conform to the lease contract, the lessee may reject or accept the goods or accept any commercial unit or units and reject the rest of the goods.

(2) Rejection of goods is ineffective unless it is within a reasonable time after tender or delivery of the goods and the lessee seasonably notifies the lessor.