The shoulder strap can be attached simultaneously.
.The HLD‑10 gives you all the camera controls you need to shoot reliably and comfortably in portrait and landscape orientation. You can also attach the optional Grip Strap, GS‑5 (optionally available) for an enhanced fit when using a telephoto lens. HLD-10 Power Battery Holder Perfectly integrated in the OM SYSTEM OM‑1 design the HLD‑10 offers you an IP53 weather sealing and is freezproof(down to ‑10°C).