A protective cover for an insertion probe of a medical instrument. The cover contains a flexible tubular body that compliments the probe geometry and a radially disposed flange that surrounds the proximal end of the body. A series of snap-on fasteners removably connect the cover to the instrument. A camming surface is located on the outer face of the flange which coacts with a cam follower that is movably mounted upon the instrument to flex the cover sufficiently to open the fastener and release the cover from the instrument and move the cover axially toward the distal end of the tip.