Microcentrifuge tube

An improved lid for a test tube, said test tube having a sealed bottom, an open top having inner and outer edges, said tube also having an inner surface and an outer surface, and a lid shaped to fit into the open top of the tube, said lid having an upper surface and lower surface, said lid also having a rim attached to the upper surface of the lid, said rim extending over the top of the test tube when the lid is covering the test tube, said rim having an upper surface and a lower surface, said lid having top and bottom surfaces and said lid having a plug connected to and extending from the bottom surface of said lid, said plug having an inner and outer surface, an upper portion attached to the bottom surface of the lid and a lower portion distal from said bottom surface, said plug being insertable into the tube when the lid is shut onto the open top of the tube, wherein the improvement comprises:

• a flange connected to and extending vertically downwardly from the lower surface of the rim of the lid, said flange being at least approximately three sixteenths (3/16) of an inch (4.7 mm) wide and wherein the flange is as long as or longer than the plug.