A tip cap includes a closed distal end portion having a transverse proximal surface, a peripheral skirt extending in the proximal direction from said proximal surface and having an inner surface designed to cooperate with the outer surface of the injection device tip, a nipple protruding from said proximal surface and designed to engage the injection device tip. The inner cavity of the tip cap is such that the outer fillet has a radius of curvature ranging from 0.4 to 0.6 mm, the inner fillet has a radius of curvature ranging from 0.25 to 0.35 mm, the nipple base width ranges from 1.4 to 1.6 mm, and the dome-shaped proximal portion of the nipple has a radius of curvature ranging from 0.55 to 0.70 mm.
