the manufacturer designed and intended to build, but the plaintiff is contending that the design itself is defective. The Third Restatement expressly prefers to measure defective design in terms of whether the product design's risks outweigh its benefits, and expressly deprecates the consumer expectations test associated with Section 402A of the Second Restatement. As noted above, state courts either use one test or the other or both. The Third Restatement also places the burden of proof on the plaintiff to prove that risks outweigh benefits by proving the feasibility of a safer alternative design. Failure-to-warn defects arise in products that carry inherent nonobvious dangers which can be mitigated through adequate warnings to the user, and which are present regardless of how well the product is manufactured and designed for its intended purpose. This class of defects also includes failure to provide relevant product instructions or sufficient product warnings. Theories of liability In the United States, the claims most commonly associated with product liability are negligence, strict liability, breach of warranty, and various consumer protection claims. Breach of warranty Warranties are statements by a manufacturer or seller concerning a product during a commercial transaction. Warranty claims historically required privity between the injured party and the manufacturer or seller; in plain English, they must be dealing directly with one another. As noted above, this requirement was demolished in the landmark Henningsen case. Breach of warranty-based product liability claims usually focus on one of three types: Breach of an express warranty, Breach of an implied warranty of merchantability, and Breach of an implied warranty of fitness for a particular purpose. Express warranty claims focus on express statements by the manufacturer or the seller concerning the product (e.g., "This chainsaw is useful to cut turkeys"). The various implied warranties cover those expectations common to all products (e.g., that a tool is not unreasonably dangerous when used for its proper purpose), unless specifically disclaimed by the manufacturer or the seller. They are implied by operation of law from the act of manufacturing, distributing, or selling the product. Claims involving real estate (especially mass-produced tract housing) may also be brought under a theory of implied warranty of habitability. Negligence A basic negligence claim consists of proof of a duty owed, a breach of that duty, the breach was the cause in fact of the plaintiff's injury (actual cause) the breach proximately caused the plaintiff's injury. and