This Super-O Boyer watch band is designing for 2009 onward Seiko Tuna models such as SBBN013 or other 21.5mm lug Seiko diver or sport watch case with straight lug. Super-O Boyer watch band is a new breakthrough of our O Boyer Collection. Same as O Boyer, this Super-O Boyer composed of 3 flat and solid 316L stainless steel units plus highlighted 3D effect curved solid end pieces. This well-built replacement bracelet was assembled by screw-in adjustable details instead of flimsy pressure pins. Watch band is tapering to 18 buckle width (compatible with original Seiko 18 buckle, if you want to install your original Seiko clasp, please check the size of your Seiko clasp first).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. Here introduce the latest technology of metal coating - "Diamond-like carbon" DLC coating. DLC is very resistant to abrasive and adhesive wear making it suitable for use in wristwatch accessories that may experience extreme contact pressure in rolling or sliding contact. The extreme hardness, wear-resistance, and slickness of DLC coating make it an ideal coating to apply to stainless steel watch bands. Accompany with V-Clasp double lock buttoned diver's clasp. V-Clasp was made from solid 316L stainless steel with extra 6 micro holes for flexible fine tune length adjustment. Featured in V shape safety lock, streamlined form & chamfer edged design to giving a more massive look. Chamfer double locks diver's buckle is ideal for watch band with thickness approximate 4.0 - 5.0mm thickness. Today replaces your Seiko Tuna into this unique aftermarket watch band.