To prove strict liability for a product defect P must show: (1) D is a merchant; (2) the product is defective- three types manufacturing defect- product differs from all others that came off the line; information defect- inadequate warnings on products with risks that cannot be designed away; design defect- design that a reasonable person would not have put on the market (P must show alternative design that is (1) safer than product marketed, (2) economically feasible, and (3) practical- not difficult to use) (3) product has not been altered since it left D's hands (presumed) (4) P was using the product in a foreseeable manner at time of injury