The NOMOS Tetra Basalt, bearing the reference 440.SB, is a distinctive model from the Tetra Origins collection featuring a closed case back. This timepiece showcases a square stainless steel case measuring 29.5mm on each side, complemented by an anthracite dial. The watch features elegant rhodium-plated hour and minute hands, along with a standout yellow seconds hand, all powered by the hand-wound DUW 4001 caliber. Among the four variants in the Tetra Origins line—Ochra, Terra, Salvia, and Basalt—this edition stands out as the darkest.

Measuring 29.5mm in width, 29.5mm in height, and 6.5mm in thickness, the case extends to a lug-to-lug length of 40.5mm. It is securely held together by four screws and showcases a sapphire crystal on the front and a closed stainless steel back. The Tetra's iconic double lugs enhance its design, while its water resistance rating of 5 atm ensures durability. The anthracite dial features a unique combination of numerals and markers, alongside a square minute track and a small seconds display positioned at 6 o'clock. The sub-dial incorporates hints of fuchsia and yellow, creating a vibrant contrast with the darker tones. The watch comes with a beige vegan velour remborde strap with an 18mm spacing between lugs.