V2 Model Pen have the "injecthru" feauture with a hole and a retractable ring on the pen cap end. This allows for sight-free needle andministration. For researchers with needle apprehension, this unique feature will conceal the needle during administration. They only come in 60 unit standard version. 2 V2 Pens (Red and Silver) 5 - 3ml individually wrapped empty Cartriges