Provided herein are fluid handling tubes having a cap that includes a sealing member having interior grooves and panels. Also provided herein are fluid handling tubes having a cap that includes (i) a sealing member having a concave surface at a distal region, and (ii) a flat proximal surface. Provided also are fluid handling tubes having a cap that includes an engagement member at an edge of the cap, where the engagement member includes a surface having curvature and a taper. Also provided herein are fluid handling tubes that include a cap comprising a tube sealing member, an anterior engagement member, and one or more channels (e.g., one or more furrows or grooves) between the sealing member and the engagement member that function as a hinge or pivot. Also provided are fluid handling tubes that include (i) a cap having a sealing member that includes an annular protrusion, and (ii) a tube body having an interior surface that includes an annular recess, where the annular recess in the tube body is configured to receive the annular protrusion of the tubular sealing member of the cap.