Version II Gearbox: M4 / M16 / 614 / S-System / G3 / MP5...ect are all Version 2 gearbox. Manufacture: JG / APS / Matrix Review: Don't be fooled by the price, these wiring / switch assembly are rated to be one of the most reliable by technicians directly from JG manufacture. Many brands are known to have melting switch when the gearbox is abused, but not from JG brand right?