The Seiko Prospex 'Sumo' SPB0101J1 case is made from 316L stainless steel and it has been hardened in Seiko's scratch-resistant DiaShield coating.  It measures 44mm in diameter, which places this watch in the midsize range, allowing it to sit comfortably on a range of wrists. The watch's curved lugs also allow it to hug the contours of the wearer's wrist. The screw-down crown is located at 4 o'clock, which is feature common amongst many of Seiko's most iconic diver watches, because it permits great comfort when on the wrist and also additional practicality when it comes to preventing it getting knocked out of place.

A 120-click unidirectional stainless steel bezel sits proudly on top of the case. The bezel displays a 60-minute scale with a luminescent pip present at the 12 o'clock marker, the bezel has been highly polished which bestows it with a glossy appearance. Similarly, the easy-to-grip coin-style bezel has also been treated to the same polished finish. On the back of the case there is a screw in solid case back which ensures the watch is water resistant. The Seiko Wave logo is engraved into the case, which serves as a reminder of this watch's intended purpose. Sapphire crystal glass provides the watch with superlative scratch resistance and protection.

The Dial:

The dial of the SPB101J1 is presented in matte black. The simplistic layout of the dial ensures optimum legibility and avoids the risk of any complications. It consists of applied polished hour markers and an equally bold handset consisting of an short pointed hour hand and baton-style minute hand. Both the indices and handset have been filled with a luminescent material, allowing the wearer to read the time in the dark.

The date window at 3 o’clock gives the watch a classic divers feel, the neat positioning does not comprise the watch’s quintessential appeal. Around the age of the dial is a subtle black chapter ring that displays a 60-minute scale. The Seiko logo is presented in white beneath the 12 o’clock marker.