GemFan produces some of the finest propellers for Multi-Rotor use, and they are available in a variety of colors and materials. All of the different sizes are available in both normal and reverse rotation as needed for use in multi-rotor craft. The standard props are made from ABS plastic with a glass fiber fill for extra strength and durability, and come in Black, Green and Orange colors.
The 4x2.5 is a GWS-style prop; the hub thickness is narrower than the 4x4.5 EPP-style prop set. The 4x2.5 props have a 5mm hole drilled in the front side of the hub. Included with the prop is a set of OD adapter rings that step down the center hole of the prop to allow it fit on 2mm, 3mm, or 4mm motor shafts. If you have a larger threaded shaft on your prop adapter, the center hole can be reamed out to a larger size as needed.