The Phase 5 Rifle Length Mini Stock Assembly (brand part number RMSA) combines the company’s Universal Mini Stock (UMS) with a rifle-length HexOne buffer tube in one combo kit, giving AR-15 and AR-10 builders a complete fixed-stock solution rather than two separate purchases. Phase 5 precision machines both pieces in-house from USA-sourced raw billet aluminum, cutting the HexOne tube from 7075-T7 and the UMS from 6061-T6. The buffer tube’s hexagonal profile is noticeably thicker and more rugged than a standard mil-spec receiver extension, while the UMS’s smaller footprint and bottom curve anchor the stock against the chest for a faster, easier transition in and out of position.

Key Specifications

• Combo kit pairing the Universal Mini Stock (UMS) with a rifle-length HexOne buffer tube.
• UMS is also compatible with mil-spec carbine receiver extensions and most round tubes.
• Precision machined in-house from USA-sourced billet aluminum.
• HexOne buffer tube is cut from 7075-T7 aluminum.
• UMS is machined from 6061-T6 aluminum.
• Buffer tube uses a hexagonal profile, thicker and more rugged than a mil-spec tube.
• UMS features a smaller footprint and bottom curve for a more stable chest anchor.
• Built for rifle-length AR-15/AR-10 platforms.
• Made in the USA.

Frequently Asked Questions

Does the UMS only work with the HexOne buffer tube? No, it’s also compatible with mil-spec carbine receiver extensions and most round buffer tubes.

What makes the HexOne tube different from a mil-spec tube? Its hexagonal profile is noticeably thicker and more rugged than a standard mil-spec receiver extension.

What material is this kit made from? Billet aluminum, machined in-house in the USA — 7075-T7 for the buffer tube and 6061-T6 for the UMS.

Buy the Phase 5 Rifle-Length Mini Stock Assembly, Black Aluminum, AR-15/AR-10

Buying a stock and buffer tube separately means gambling on fit, and this Phase 5 combo kit removes that guesswork for a rifle-length build. Browse the rest of our rifle stocks selection and order from our Lubbock, Texas gun shop — we’ll get it moving as soon as it’s ready to ship.