CNC Aluminum 6717451-R Reversed 4 Blade Magnalium 7075 propeller. Hardened for strength. Machine-cut to high tolerances, this prop is ready to use right out of the box. The Magnalium 7075 alloy makes this material upwards of 30% stronger than standard 7075 aluminum. ATTENTION: Right and rotation. These spin clockwise when viewed from the back of the boat. Used for twins or boats that require opposite rotation than normal. See picture. Fits 1/4"(.250" 6.35mm) Smooth Bore Propeller Shafts.