4 inch propeller (2 inch radius) mounted on a 1/2 inch stainless steel shaft. It is not mounted right at the bottom, this is done to prevent the blade from contacting the bottom of the bucket during mixing. By googling the identification you see on this prop(Taiwan 4x4 316 propeller) you would find the site of the manufacturer (http://www.tonson-motor.com/e/p004.htm).
A One-speed Lab or Studio Slurry Mixer
Sign up at the home page.