Roto-Lith, Ltd. (Roto-Lith) (plaintiff) offered to buy an emulsifier manufactured by F.P. Bartlett & Co., Inc. (Bartlett) (defendant), for use in making Roto-Lith's "wet" cellophane bags. Bartlett sent Roto-Lith a letter acknowledging Roto-Lith's order. The acknowledgment added a no-warranty clause disclaiming Bartlett's liability should the emulsifier prove unsatisfactory for use in wet bags and requiring Roto-Lith to protest promptly if Roto-Lith did not assent to the no-warranty clause. Roto-Lith made no such protest. Bartlett shipped the emulsifier to Roto-Lith, which accepted and paid for the emulsifier. The emulsifier was designed for "dry" bags and proved unsuitable for wet bags. Roto-Lith sued Bartlett in the United States District Court for the District of Massachusetts. The case was governed by Massachusetts law, which incorporated section 2-207 of the Uniform Commercial Code (UCC). Roto-Lith contended that Bartlett's no-warranty clause materially altered the terms on which Roto-Lith offered to buy Bartlett's emulsifiers. Roto-Lith further argued that the no-warranty clause was only a proposal that was never included in the parties' sale contract and, thus, was no defense against Roto-Lith's suit. Nevertheless, the court directed the jury's verdict for Bartlett. Roto-Lith appealed to the United States Court of Appeals for the First Circuit.