Abstract: A single cavity specimen test tube carrier especially adapted to connect to like carriers along one axis or a different axis or in a matrix. The carrier includes a test tube holder, a viewing slot, a side-to-side coupling mechanism and a front-to-back joining mechanism to attach the carriers together along a specified axis or in a matrix. The side-to-side coupling mechanism includes a boss and boss receiving cavity which snap together in a force fit. The front-to-back joining mechanism includes a plurality of knob-like protrusions that fit snugly into the viewing slot of an adjacent carrier and a horizontal bar that slides under a corresponding ledge of the adjacent carrier.