Originally the P90 was available in one version. It was fitted with a reflex sight and no accessory rails. The P90 is fitted with a HC-14-62 or MC-10-80 reflex sight. In the mid 2000's the designation was changed to P90 Standard with certain elements of the P90TR being available, such as side mounted accessory rails and LV and LIR attachments. The P90 USG is fitted with a similar sight unit as the P90, but has a black reticle that does not require daylight.

The P90TR is similar to the original P90 except for the sight unit. TR stands for Triple Rail as instead of the integrated sight three Picatinny accessory rails are fitted. This allows various optics and attachments such as lasers and lights to be fitted. In the mid 2000's the designation was changed into P90 Tactical. The P90TR is also available as the P90LV and P90LIR with an integrated visible laser and IR laser respectively.

The PS90 is a civilian model of the P90 that was developed for the US civilian market. It was introduced in 2005. The PS90 is semi-automatic only and has a much longer barrel that extends from the weapon. The standard 50 round magazine can be fitted, but the PS90 is only sold with 10 or 30 round magazines. The PS90 is available with the Standard, USG and TR sight units.