A coupler assembly for connecting to a nipple, the coupler assembly comprising: a valve housing; a valve that is moveable within the valve housing between a first valve position in which the valve is closed, and a second valve position in which the valve is open; a ball body that is fixed to the valve housing and defines a ball slot; at least one locking ball that is received within the ball slot and is moveable between two opposing side walls of the ball slot; a locking sleeve that is located radially outward relative to the ball body, wherein the locking sleeve is configured to interact with the at least one locking ball to lock the valve in the second valve position when the coupler assembly is connected to the nipple; and a slider that is positioned radially between the ball body and locking sleeve, and longitudinally inward relative to the at least one locking ball; wherein during a connection operation to connect the coupler assembly to the nipple, the slider is moveable along the ball body between a first slider position and a second slider position to permit movement of the at least one locking ball within the ball slot to permit insertion of the nipple when the valve moves from the first valve position toward the second valve position, and the slider is biased to return to the first slider position when the valve is in the second valve position, and wherein during a disconnection operation to disconnect the coupler assembly from the nipple, the locking sleeve is longitudinally moveable relative to the ball body between a first sleeve position and a second sleeve position to permit removal of the nipple from the coupler assembly; wherein the coupler assembly further comprises an interface seal located adjacent to a longitudinal outward end of the valve, wherein the interface seal is configured to slide along an inner surface of the ball body during the connection operation, the interface seal including a stiffening washer, wherein the nipple includes a nipple nose that circumscribes the outward end of the valve when connected, wherein the nipple nose engages the interface seal and interacts against the interface seal to move the valve longitudinally during the connection operation to move the valve from the first valve position toward the second valve position and the stiffening washer prevents wear of sealing material of the interface seal as the interface seal slides along the inner surface of the ball body. a valve housing; a valve that is moveable within the valve housing between a first valve position in which the valve is closed, and a second valve position in which the valve is open; a ball body that is fixed to the valve housing and defines a ball slot; at least one locking ball that is received within the ball slot and is moveable between two opposing side walls of the ball slot; a locking sleeve that is located radially outward relative to the ball body, wherein the locking sleeve is configured to interact with the at least one locking ball to lock the valve in the second valve position when the coupler assembly is connected to the nipple; and a slider that is positioned radially between the ball body and locking sleeve, and longitudinally inward relative to the at least one locking ball; wherein during a connection operation to connect the coupler assembly to the nipple, the slider is moveable along the ball body between a first slider position and a second slider position to permit movement of the at least one locking ball within the ball slot to permit insertion of the nipple when the valve moves from the first valve position toward the second valve position, and the slider is biased to return to the first slider position when the valve is in the second valve position, and wherein during a disconnection operation to disconnect the coupler assembly from the nipple, the locking sleeve is longitudinally moveable relative to the ball body between a first sleeve position and a second sleeve position to permit removal of the nipple from the coupler assembly; wherein the coupler assembly further comprises an interface seal located adjacent to a longitudinal outward end of the valve, wherein the interface seal is configured to slide along an inner surface of the ball body during the connection operation, the interface seal including a stiffening washer, wherein the nipple includes a nipple nose that circumscribes the outward end of the valve when connected, wherein the nipple nose engages the interface seal and interacts against the interface seal to move the valve longitudinally during the connection operation to move the valve from the first valve position toward the second valve position and the stiffening washer prevents wear of sealing material of the interface seal as the interface seal slides along the inner surface of the ball body.