10 inches round X 4 inches high.  
For best results cover foam cake dummies with piping gel to help fondant adhere to the foam.
Important note about shipping:
foam cake dummies are easily dented and nicked.  When we pack them up for your order, we do take care packaging them to make sure your foam cake dummies arrive in good condition. Should your foam dummies arrive with imperfections, please use royal icing or fondant to cover any dents or nicks.