First introduced in September 2002, ZipZaps were an instant success and one of the most popular gifts of the holiday season in North America, with RadioShack stores often selling out of the starter kits. They were referred to as "micro R/C" due to their diminutive size. At around , ZipZaps were only slightly larger than popular die-cast toy cars such as Hot Wheels and Matchbox.ZipZaps were unique among toy-style micro R/C vehicles in that they could be customized much like large R/C models. Each partially assembled ZipZaps kit included a pre-assembled chassis with built-in nickel metal hydride rechargeable batteries on which the gears, tires and hubcaps could be changed for better appearance and performance. Six motors and three gear ratios were offered, ranging from the 10,000 rpm "precision control motor" to the high-speed 34,000 rpm "NX" (named after a popular brand of nitrous oxide). Gear ratios were 12:1 "stock", 9.86:1 "performance" and 8.25:1 "turbo". Tracking was adjusted via a wheel alignment lever underneath the vehicles themselves. The vehicle's on-board battery was charged by snapping the entire car onto the top of the transmitter. Full charge was accomplished in about 40 to 60 seconds with run times averaging five minutes. Neither steering nor throttle was proportional, with both functions either full on or full off. The SE series added semi-proportional, two-speed throttle and fully proportional rack-and-pinion steering with steering trim adjustable at the transmitter, as with a full-sized R/C.