The 9W Pilot Diode Lasers hand-pieces (or attachments) were named 5W and 3W for simplicity. When using the laser on a Continuous Wave (CW) power setting of 5 Watts, you would ideally use the 5W (larger) hand-piece for 5 minutes to treat an area the approximate size of a playing card to achieve the most effective treatment. When using the laser on a Continuous Wave (CW) power setting of 3 Watts, you would ideally use the 3W (smaller) hand-piece for 5 minutes to treat the same size area. To put it simply, the names came from the settings (5W setting, 5W hand-piece for 5 minutes or 3W setting, 3W hand-piece for 5 minutes). The power setting should be adjusted higher or lower based on the depth of penetration desired, skin pigment, hair obstruction and hand speed.