The RS Regulate Full-Length Modular Lower (part no. AK-303M) clamps to the side rail on most Eastern European AK rifles and forms the base half of the RS Regulate AK-300 Modular Side Mount System. It uses a quick detach mounting interface. RS Regulate began rolling out the AK-300 Modular Side Mount System in 2012. The system now spans six fully modular uppers and nine different lowers covering most Eastern European AK side rails, Yugo/Serbian-pattern rifles, PSL and Romanian M10/RH10 rifles, the Century Arms proprietary side rail, and Czech vz. 58s. This lower does not include an upper; it pairs with any RS Regulate modular upper — Aimpoint Micro, Trijicon RMR, Trijicon ACOG, Trijicon MRO, or a 1913 Picatinny rail — so a shooter can standardize one side-rail base across several optics.

Key Specifications

• Mounts to the side rail on most Eastern European AK rifles.
• Uses a Quick Detach mounting interface.
• Coverage is full-length along the receiver.
• Part of the RS Regulate AK-300 Modular Side Mount System, introduced in 2012.
• The system spans six modular uppers and nine lowers covering most AK variants.
• Accepts any RS Regulate modular upper (sold separately) to complete the optic mount.

Frequently Asked Questions

Does this include an optic mount? No, this is the lower half only. You’ll need a compatible RS Regulate modular upper for your specific optic to complete the mount.

Will this fit my rifle? It’s built for most Eastern European AK side rails; check your rifle’s side rail pattern before ordering.

Buy the RS Regulate Full-Length Modular Lower

Standardize your AK optic mounting with the RS Regulate Modular Side Mount System. Order this RS Regulate lower from our Lubbock, Texas gun shop and pair it with a modular upper from our AK parts selection. Direct shipping, no FFL required.