The FN P90 was designed to be used in conjunction with heavy body armor, which is why most shooters find the stock length to be too short.
The Damage Industries P90 Stock Extension addresses this dilemma, providing a user-adjustable solution that is durable and effective.  

Features durable Delron extensions and pad - Aluminum Plate
This is the base product, measuring 1" in width. Fasteners included.

Some jurisdictions have imposed overall length requirements on certain firearms. The 2" extension allows the P90 to be owned in those situations.
Additional extensions, which may be used in conjunction with this assembly, are available in 1" and 2" and will fit between this pad assembly and the rifle.

Made in USA.