If your thinking of getting this for a standard C5, you should know that the fingers are missing and the armature is also broke.
http://cgi.ebay.co.uk/12-Volt-30A-DC-Motor-Controller-with-Sinclair-C5-motor_W0QQitemZ290408129488QQcmdZViewItemQQptZUK_BOI_Electrical_Components_Supplies_ET?hash=item439dac63d0
Should be ok for other things / mods though