The first reusable pen for insulin glargine 300 U/mL, Toustar, has a dedicated replaceable cartridge. The Cartridge is pre-assembled to labelled cartridge holder for easy attachment & replacement. A dedicated joint interface between the cartridge holder & pen body is intended to mitigate the risk of users using other insulin cartridges. The Penalty-free dose correction feature allows to correct an over-dialed dose with a needle fitted without wasting the insulin dose. The Mechanical last dose stop prevents dialed dose from exceeding the remaining content and reduces the risk of underdosing. The pen is more compact compared to the other reusable pens available in the Indian market and has the least weight and therefore may be more user friendly.