The D550 is powered on and off with a magnetic tail switch. Complete with 18650 Battery, USB Charger, Handmount, Lanyard & Spare O-ring. D550 would be qualified for both recreational diving as a primary light and deep diving as a backup light.
Lumens: 970 (high), 367 (low), 970 (strobe mode)
Burn time: 2 hours (high), 5 hours 45 min (low)
LED: Cree XM-L2 (U4)
Depth rating: 150m
Weight: 183g (excluding battery)
Size: 144mm x 25.4mm x 40mm