The crank to shaft connection is an advanced square plug in square hole for high strength and a positive contact eliminating any slop or bang in pedaling. The cranks are advanced aluminum alloy for high strength and light weight.Modifications to the regulation voltage and current are available upon request, such as 16.8 volts for direct charging of lithium four cell batteries of 24 volts for electric bicycle or other six cell lithium applications. Substituting the included accessory for a different accessory such as the 12 volt to dual 3.1 amp USB are also available upon request. See K-Tor website for additional information and video demonstration. This is a bundle of the Power box 50 and the PS USB. The PS USB is a hand crank generator that delivers 1 amp to a standard USB interface. It is 15 oz and 7 inches long. About the size and weight of a water bottle. The item "Power Box 50 emergency kit, bundled with Pocket Socket USB hand crank" is in sale since Monday, September 16, 2019. This item is in the category "Sporting Goods\Outdoor Sports\Camping & Hiking\Emergency Gear\Other Emergency Gear". The seller is "ktorino802" and is located in Clayton, North Carolina. This item can be shipped worldwide.