Specna Arms PRIME™ H-series, i.e. HK416 type airsoft guns, are equipped with a full metal lower frame. The frame is compatible with the new ESA2.1 (2024) quick-change spring system.
The frame is fully compatible with H Edge and Edge 2.0 series upper frames, but the frame requires a dedicated ESA2.1 (2024) compatible spring guide.
https://www.atom-airsoft.fi/tuote/specna-arms-esa-2-1-jousenohajanin-prime-2024/
