These rotors are made for DIY projects like a pulsed permanent magnet motor and other things. The rotor is 9.5" in diameter, and there are 12 holes cut out for 3/4" round permanent magnets. The permanent magnets can be 3/4" or 1" long. The holes are cut out tightly, so a wooden block may be used to push the magnets into place. Also, the permanent magnets can be permanently glued in. The center hole for the shaft is 1/2" for a 1/2" shaft. The rotors are made out of HDPE (high density polyethene) that is 3/4" thick. ONLY HDPE ROTOR IS INCLUDED, AND PERMANENT MAGNETS ARE NOT INCLUDED. THE PRODUCT MAY SLIGHTLY DIFFER FROM THE IMAGES.