The N size battery, also known as LR1, E90 or MN9100, is a small cylindrical battery commonly used in various small electronic devices such as calculators, remote controls, and medical devices. It is one of the smallest Alkaline batteries available, measuring 12mm in diameter and 30mm in length.

The N size battery has a nominal voltage of 1.5 volts and is commonly made of Alkaline chemistry. It has a relatively low capacity compared to larger batteries, but it is suitable for low-drain devices that require a small amount of power over a long period of time. The N size / Lady battery is typically designed to be used in low-drain applications, such as remote controls or small electronic devices, where a high capacity is not required. It has a relatively long shelf life and can be stored for several years without losing its charge.