What goods did the Soviet Union provide to Britain and the United States under reciprocal aid?
Short answerMostly raw materials and some precious metals, with a few specialized technical contributions such as cordite samples for research.
NotesThe Soviet Union mainly sent raw materials and some precious metals westward. The discussion also notes specialized exchanges, including cordite samples used in American flamethrower research. This narrower flow was much smaller than the volume of aid sent to the Soviet war effort. The answer preserves the reciprocal principle without pretending the two directions were equal in scale or composition.