The NiteCore D10 SP and EX10 SP are new versions of the popular D10 and EX10. While the previous models had adjustable brightness, the SP versions give you three useful levels and add strobe and SOS. The small size and excellent knurling are still in place, as is the piston drive. The piston drive is a metal sleeve that goes the full inside length of the battery tube to make contact with the head, giving you a more reliable switching mechanism than the traditional switch.