P was injured when the pickup he was driving was hit from behind by a 1978 General Motors Corporation (GMC) two-ton chassis-cab, which had been equipped with a water tank after sale by the GMC dealer. P sued D on a theory of strict liability. P maintains the product was unreasonably dangerous because of both manufacturing and design defects. The parties stipulated that the accident occurred because of brake failure. Expert testimony from both parties established that the fluids necessary to the braking system had escaped when a brake tube came out of a nut where it fastened to the top of the Hydrovac, a booster unit. Witnesses also testified that the brake tube came out of the nut either because the tube broke or was improperly flared. P contends that the tube broke because there was a manufacturing defect in the tube when the truck came off the assembly line. P also contends that the brake system on the truck, a single system, was defectively designed, and argues that D's knowledge of available technology coupled with the foreseeable use of the vehicle should have mandated a dual braking system, which provides extra braking power. P maintains the accident would have been less severe or would not have happened had the truck been equipped with a dual system. D contends that the tube had been altered after it left the assembly line so that the defective tube was not D's responsibility. D also contended that the single system was neither a design defect nor unreasonably dangerous and that the accident would have occurred even if the truck had been equipped with a dual brake system. P appealed a jury verdict for D in that the jury was not properly instructed on manufacturing defects.