This Hexad watch band with a curved solid end pieces perfectly fit Seiko MM300 Prospex Marinemaster SBDX001 / SBDX003 / SBDX005 / SBDX017 models. Hexad watch band is a striking design first launched in recent years. Each link is composed of 3 massive Chamfer edge solid 316L stainless steel units and a curved solid end piece. Hexad is a contemporary version of the traditional O Boyer watch band, but more thick & sturdy over 100 grams. Considering the comfort and sustainability, it bends smoothly following your wrist. Well-made solid 316L stainless steel links are assembled with screws instead of flimsy pins to keep its solidity and stability. The lug of this watch band was tapered into 18 buckle size, added value on flexibility of using your original 18 Seiko clasp back if you want. The lug of this watch band was tapered into 18mm buckle size, added value on flexibility of using your original 18mm Seiko clasp back if you want. This item includes one pair of FAT spring bar (Generic Seiko Dia. 2.5mm spring bar) to ensure a more secure connection. Accompany with ratchet buckle clasp which is an ideal wetsuit watch band buckle. The ratchet theory extension mechanism is of great importance for both convenience and safety. Hexad watch strap is a good choice of Seiko watch band replacement for your MM300 Prospex Marinemaster SBDX001 / SBDX003 / SBDX005 / SBDX017 models.