Abstract: A hand tool for slitting tubes longitudinally comprising a main tubular body section having an axial passage of uniform diameter provided at one end with a cutting blade which extends radially into the axial passage and at the opposite end with a roller guide member which extends into the axial passage for engagement with a tube in the passage to prevent relative rotary motion about a longitudinal axis between the tube and the body section of the tool. The main tubular body section is adapted to have removably secured in the axial passage thereof a tubular insert member which has an enlarged end section with a passage extending therethrough coaxial with the axial passage of the main body section and which is also provided with a roller guide member extending into the axial passage therein.