Refusal to accept performance preserves promisor rights when a valid offer of performance is duly tendered and inspectable. Refusal to accept an offer of performance does not make the promisor liable for non-performance or forfeit contractual rights if the promisor has validly tendered performance. A valid offer must be unconditional, made at a proper time and place, and permit the promisee a reasonable opportunity to verify ability and willingness to perform; where delivery is involved, the promisee must be able to inspect that the thing tendered matches the contractual specification.