Ratchet Buckle Clasp is an ideal Wetsuit watch band buckle. The ratchet theory extension mechanism is of great importance for both convenience and safety. Super-O Boyer watch bracelet is composed of 3 flat and solid 316L stainless steel units and a curved solid end piece perfectly fit Seiko MM300 Prospex Marinemaster SBDX001/SBDX003/SBDX005/SBDX017 models. Screw-in adjustable details instead of pressure pins. This item includes one pair of FAT spring bar (eg. generic Seiko Dia. 2.5mm spring bar) to ensure a more secure connection. Tapered 20mm lug into 18mm buckle size. Super-O Boyer watch bracelet is a good choice of Seiko replacement watch band for your MM300 Prospex Marinemaster SBDX001/SBDX003/SBDX005/SBDX017 models.