This is one serious dive light. The 4100 is submersible to 150 meters with an ABS body, polycarbonate lens, and thermoplastic shroud. All corrosion proof and chemical resistant. Two reflectors are included: a modified spot (stippled for a wide beam) and a laser spot (smooth for a tight collimated beam). Also, a back-up lamp is stored behind the reflector for emergencies. The dual direction switch is easy to operate, even with thick gloves. And there's a locking slide feature to prevent accidental activation. The pistol grip/lantern handle quickly converts to multiple positions for flexibility. The Nemo 4100 also comes with a shock absorbing internal battery module that protects both the cells and the lamp from hard knocks. Powered by 8 D alkaline cells.