Abstract: A mounting for a supply reel and a take-up reel in a camera, projector or other recording or reproducing apparatus comprises two coaxially juxtaposed mandrels of substantially the same diameter cantilevered for independent rotation on a common support. The outer mandrel carries one or more radially retractable detents whose withdrawal from a projecting position enables the take-up reel to be fitted onto the inner mandrel and which thereafter form a stop for the supply reel, thereby preventing the two reels from contacting each other. The withdrawal of the detents, or the removal of an abutment blocking such withdrawal, may be carried out as a separate operation; alternatively, withdrawal may be blocked automatically upon the emplacement of a reel on the inner mandrel.