BD Ultra-Fine Pen Needles 4MM 32G:
Insulin is meant to be injected into the fat layer just below the skin for consistent absorption. If you inject into a muscle, the insulin can work too quickly, which may lead to low blood sugar. 
The BD Nano™4mm Pen Needle, BD’s shortest pen needle gets insulin to the fat layer over 99.5% of the time, at all injection sites.

Key benefits:
BD's smallest, thinnest pen needle.
EasyflowTM technology for less effort to injection.
PentaPointTM Comfort for a smoother, gentler injection experience.