Number of Stereoisomers of C(CHClCH3)4 I am having trouble understanding why the structure 

$$\ce{C(CHClMe)4}$$

has only five stereo isomers. According to my textbook, the stereo isomers correspond to the following series of absolute configurations:


(R,R,R,R)  
(R,R,R,S)  
(R,R,S,S)  
(R,S,S,S)  
(S,S,S,S)


But my question is, does not the order in which these appear change the total? Isn't (R,S,R,S) different from (R,R,S,S)?
To answer your question, if you haven't figured it out by now, RRSS is the same as RSRS and it is the only one of the five that is optically inactive (Compare with nonactin). Structure A numbers the positions of chiral chlorine-bearing carbons. Structure B is RSRS and C is RRSS. Clearly, they are superimposable and, therefore, identical. A similar exercise with RRRS and RSSS will give a similar result.