The Beretta BU-9 Nano is a semi-automatic, striker fired, micro compact pistol line manufactured by Beretta of Italy. The initial design was created for a .40 S&W round but the initial release is chambered in 9mm. It has been available since October 2011.
The Nano is designed as a compact gun for concealed carry. It has a technopolymer frame and a Pronox finished slide. Pronox is a nitriding finish similar to Tenifer (as used on, among others, Glock pistols) and Melonite (as used on, among others, Springfield Armory XD and Smith & Wesson M&P pistols). The sights on the Nano are low-profile 3-dot sights. It is currently not available in California.
The 9mm version of the Nano holds 6 rounds of 9mm in a single-column box magazine, for a total capacity of 7 if the pistol is chambered and the magazine is fully loaded. The .40 S&W version of the pistol is designed to have an identical 6+1 capacity.
The Nano was designed with a serial-numbered chassis separate from the frame, an unusual feature notably also found in the Sig Sauer P250-series pistols. This will allow Beretta to provide additional frames in the future, allowing for a variety of grips and colors. The chassis is removable and can be placed in the alternate frames.