The Leofoto P Series Arca-Type Plates are designed for compatibility and stability, while providing a secure connection for your ball head and fluid heads. These are compatible with any arca-type clamp. Crafted from Type II Black hard anodized, 6061-T6 aluminum these base plates are built to last. In addition to the 3/8" mounting screw, there are two M6 anti-twist set screws to keep the head in place. P-LH40: 57x40mm/ 2.24x1.57in P-LH47: 62x40mm/ 2.44x1.57in P-LH55: 72x40mm/ 2.83x1.57in P-BV10: 60x40mm/ 2.36x1.57in P-BV15: 70x40mm/ 2.75x1.57in