Mr. Pen mechanical calculator combines precise everyday calculating with satisfying mechanical switches and a fresh, desk-friendly look. 12-digit capacity — ideal for handling calculations with precision and ease. Large LCD display — clear, easy-to-read numbers for accurate inputs and outputs at a glance. Mechanical switch keys — tactile, responsive presses that feel smooth and satisfying. Round, colorful buttons — big, comfortable keys with an eye-catching aesthetic. Lightweight & portable — easy to carry and use at home, school, or the office. Auto shutoff after 10 minutes — helps conserve battery life and supports long-lasting use. Battery powered — operates on one AAA battery (not included) .