letter keychain 3d model

Create a precise 3D printable keychain based on the uploaded capital letter "B". Preserve the exact proportions, stroke thickness, rounded corners and typography of the reference image. The model must be flat on both front and back faces with a uniform thickness of 5 mm. Overall height 55 mm. Include a circular keyring hole (4.5 mm diameter) centered above the letter with 3 mm edge clearance. Smooth edges with a small 0.8 mm fillet. No textures, embossing or decorative elements. Optimize the geometry for FDM 3D printing as a single solid watertight STL.