Warne ARCA Rail M-LOK interface 4in. Whether you seek the ability to attach your rifle to a tripod the freedom to move your bipod to your desired position or use one of the many ARCA style accessories available the Warne M-LOK ARCA rail can handle it all. These rails are available in 4- 8- and 12-inch lengths. Package Contents: Warne ARCA Rail M-LOK interface Warne 6204M: ARCA Rail M-LOK interface 4in