TheE-49 Lens CapfromCanonhelps to protect the front lens element from dust, dirt, moisture, and other elements during travel and storage. It fits lenses with 49mm-diameter threads, and is offered here more→as a replacement for the cap originally included with the EF 50mm f/1.8 STM lens. Canon E-49 Lens Cap TheE-49 Lens CapfromCanonhelps to protect the front lens element from dust, dirt, moisture, and other elements during travel and storage. It fits lenses with 49mm-diameter threads, and is offered here as a replacement for the cap originally included with the EF 50mm f/1.8 STM lens.