This release plate is a must for those carrying more than one piece of mountable equipment along with a Slik Quick Release equipped tripod. This release plate make a great spare or replacement. Slik Quick Release Plates/Posts Chart for Matching to Head 618330: For 300DX, Pro330 618335: Standard; For 700DX, Pro Ball Head 800 618340: 3/8-inch; For 700DX, Pro Ball Head 800