The Z-RAM Huben GK1 stock system separates three jobs: the rear adapter provides the stock connection, the folding shoulder stock provides shoulder support, and the lower Picatinny kit provides an accessory rail. The stock requires the rear adapter, but the lower rail is a separate choice rather than a missing part of that connection. Z-RAM specifies the GK1 EU version for the rear adapter and GK1 V3 for the lower rail.
What the rear adapter contributes
The adapter is CNC-machined aluminum with a black anodized finish. Its product description says the rear sight stays in place and confirms compatibility with Z-RAM’s GK1 Picatinny and red-dot mount rails. That matters when the goal is shoulder support while retaining the existing sight arrangement: the adapter is not an optic mount and does not replace the separate rail decision.
The adapter package contains one adapter and two mounting screws. A stock-shaped assembly in a finished product photograph should not be mistaken for everything supplied in this particular box. The actual shoulder stock has its own listing and is purchased separately unless it is already owned.
Why choose the folding stock?
Z-RAM describes the shoulder stock as a way to provide an additional support point, with sideways folding to make the GK1 more compact for storage and transport. The stock is also CNC-machined, black-anodized aluminum. Its listed weight is approximately 280 g and its dimensions approximately 200 × 100 mm. Those are the stock’s figures, not the weight or dimensions of the entire airgun.
The practical difference is support versus portability: the extended stock offers a shoulder contact, while the folding mechanism reduces its projection when stored. This is an ergonomic benefit, not a promised increase in muzzle energy or a measured improvement in group size. The dedicated Huben folding-stock guide covers that mechanism in more detail.
Where the lower Picatinny rail belongs
The lower rail is listed as a trigger-guard replacement for the Huben GK1 V3. It provides a mounting interface for suitable Picatinny accessories; it is not the rear stock adapter and is not needed merely to obtain the stock connection. Its black-anodized aluminum construction matches the material approach of the rear components, but the shared finish does not erase the different fit statements.
For the purchase decision, distinguish the exact GK1 version from the accessory role. Someone who already owns the rear adapter needs the separately listed stock, not a second adapter. Someone seeking a lower mounting point needs the V3 rail assessment, not a shoulder-stock package. Huben GK1 is a PCP airgun platform, so similar-looking T4E or bottle-mounted stocks are not interchangeable evidence of fit.
Products for this decision
Buttstock Adapter | CNC ALU | black anodized | Huben GK1
Rear adapter for the GK1 EU version. Includes two screws; the folding shoulder stock is separate.
View product details
Huben GK1 shoulder stock black anodized aluminum foldable for additional Picatinny rails
Folding aluminum shoulder stock. Requires the separately sold GK1 rear adapter; approximately 280 g.
View product details
Lower Picatinny Rail Kit | Triggerguard | Huben GK1
Optional lower Picatinny rail for GK1 V3. This is a trigger-guard replacement, not part of the rear stock connection.
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