Knob for CTS288 Encoders

[TarikMerryface]

Does anyone have the dimensions of the Knob for the CTS288 Encoder that is sold by Leo Bodnar? (linked below)

I'm mostly interested in the radius of the base of the knob.

thanks!

http://www.leobodnar.com/shop/index.php?main_page=product_info&products_id=198