The AX602M500 is a multi-mode, 500 memory advanced timing stopwatch with the best wos (watch operating system) functions and features to provide you with the highest quality stopwatches available. Accusplit professional "x" stopwatch case has an ergonomic design that is immediately recognizable to anyone involved in Elite sports. Features: operating system: wos 3.0 memory: 500 memory recall (running: lifo, stopped: fifo) speed rate measurement: miles/KM stroke (per Min.): 180-10 pacer (beats/Min.): 5-240 dual split with running cumulative auto split release one-button start/rapid split action split counter 1, 2 fast finish fastest, slowest, average lap countdown timer (3 mode): 20 hours time out timing range (hours): 20 timing interval: 1/100 sec. no proof and proof of purchase resolution & accuracy limit: the internal quartz and ic controller looks at switch closure every 1/256th of a second, so that Nearest 1/100 is captured. Actual accuracy: tested and calibrated to be within 0.04 sec/hour for 12 months. Only shocks and aging of the quartz crystal affect this actual accuracy rating.