A tubular insertion aid for catheter manipulation is disclosed. The insertion aid is particularly suited for urinary catheters, such as hydrophilic urinary catheters for intermittent use. The insertion aid comprises a forward opening, a rearward opening and a slit opening extending along a part of the sidewall of the tubular insertion aid, so that a first portion of the tubular insertion aid in the axial direction forms a solid circumference around the tubular insertion aid, and a second portion in the axial direction is provided with the slit opening extending in an axial direction of the tubular insertion aid. The tubular insertion aid further comprises a first inward protrusion formed on the interior side of the tubular insertion aid in a part of the second portion being provided with the slit, wherein the first inward protrusion is arranged along a first protrusion line extending along the inward circumference of the tubular insertion aid essentially perpendicularly to the axial direction of the tubular insertion aid.