Strap for SUB 300 Carbon Professional

The Doxa SUB 300 822.70.351.21 features a lug width of 20 mm. This measurement is taken on the inner surface of the lugs—the lateral protrusions of the case at 3 o'clock and 9 o'clock positions. To verify compatibility, use a digital calliper positioned perpendicularly between the two lugs: the value must correspond exactly to 20 mm to ensure a perfect fit with your strap.

The ideal strap depends on your intended usage. For technical diving applications, we recommend FKM rubber or a moisture-resistant NATO: both guarantee full water resistance and rapid drying after immersions. For formal settings, an alligator strap with vegetable tanning or a calf leather strap with deployante adds sophistication whilst maintaining the watch's instrumental vocation. The titanium and carbon case pairs exceptionally well with straps featuring matte or satin textures, avoiding glossy finishes that would create visual conflict.

Strap replacement on the SUB 300 requires a spring bar tool. Position the watch case-down, then insert the tool's tip into the small hole on the lug protrusion, pushing gently inward: the spring bar will retract, allowing old strap removal. Install your new strap (ensuring it is exactly 20 mm) by aligning it with the lugs and releasing tool pressure so the spring bar returns to position. Verify the strap is securely fastened on both sides before wearing the watch.

Yes, you can absolutely use quality aftermarket straps compatible with your SUB 300. The critical factor is verifying that the lug width matches exactly 20 mm: any variation, however minor, will create visible gaps or prevent installation. Milano Straps provides a curated selection of professional leather, NATO, and rubber straps specifically measured for SUB 300 compatibility, allowing you to transform your watch's aesthetic without compromising construction quality.

A quality leather strap—such as those crafted in alligator or vegetable-tanned calf—typically lasts 3–5 years under daily wear, extending to 7–10 years with occasional use. Longevity depends on humidity exposure, direct sunlight, and maintenance level. To extend strap life, avoid water submersion with leather (use rubber or NATO for aquatic activities) and periodically treat with leather-specific nourishing creams. The strap will develop a natural patina over time, adding character and aesthetic depth without losing functionality.