There is also differences with regards to benefits and the amount time you are allowed to work. You are only allowed to work a certain number of Class A in any given fiscal year (I think it is 180 full days). While on Class A you are entitled to some dental benefits provided you meet certain requirements (ie trade trained, length of service completed). There are also two kinds of Class B. Class B under 180 days, and Class B over 180 days. The distinction is the benefits you can receive. Basically (I know I am simplifiing, there are always exceptions to every rule), Class B under 180 get the same benefits as Class A. Class B over 180 get more extended coverage (medical, dental, physio). Class C is you are basically seen as a regular force person (cept you were a reserve cap badge.). As was already mention Class C is the rarest contract, usually you only get Class C when you go on tour.