The ACT-310 is a separate rear standard which allows the use of shorter digital lenses from Rodenstock and Schneider to focus in combination with the Sony E-mount series cameras, such as the Sony A7/7R
ACT-310 matches the ACTUS-T version and has a built-in Sony bayonet and a built-in WA bellows (non removable). The bayonet is non-rotating as with the normal version in order to allow the short distance.