UTG Pro Model 4 S1 6-Position Mil-Spec AR-15 Stock Kit

The UTG Pro Model 4 S1 Mil-Spec Butt Stock Kit is a collapsible stock assembly designed for AR-15/M16 platform rifles. It pairs a weatherproof, high-impact polymer body with a precision-machined mil-spec aluminum extension tube for a secure, repeatable fit. The six-position adjustment and ergonomic shaping provide adaptable length of pull and improved handling. The kit ships with the extension tube, buffer, buffer spring and associated mounting hardware.

Key Specifications

• The stock is constructed from impact-resistant high-strength polymer with an aircraft-grade aluminum extension tube.
• The assembly provides 6 positions for length-of-pull adjustment.
• The finish and color are black.
• The kit includes a mil-spec 6-position extension tube.
• Included accessories are buffer, buffer spring, tear-drop ring, and castle nut.
• The stock features a thick rubberized recoil pad for added shoulder comfort.
• It provides an ambidextrous sling loop and reversible QD sling swivel housing for versatile carry options.
• Dual storage compartments with removable waterproof caps can hold up to 8 CR123 batteries or similar items.
• The extension tube uses rolled threads for a precision fit and reliable mounting.
• Design elements include chamfered edges and a slanted cheek rest for snag-free handling and consistent shouldering.

Built for shooters who value rugged construction and practical features, the Model 4 S1 Mil-Spec Stock Kit delivers reliable fit, straightforward adjustment, and integrated storage without unnecessary complexity. Its combination of polymer durability and a machined mil-spec tube makes it a sensible upgrade for range use, training drills, and adaptable AR-15 configurations where consistent performance and comfort matter.