15T Freewheel Which Works on Flip Flop Hub I am building a Single Speed Freewheel and I read somewhere that manufactures don't make 15T freewheels that fit on a Flip Flop hub; only 16t and bigger. However, I would like a gain ratio above 3 and I already purchased a 48T chain ring. 

Is it true that you can't buy 15T Freewheel that will work on a regular non BMX wheel?
The normal freewheel thread is too large for cogs smaller than 16T. One source for the information is Sheldon Brown's singlespeed page. It is a good one to read before buying any more parts.

A BMX flip flop hub will, however, take smaller freewheels that have smaller thread. Fixed/free flip flop hubs have the larger freewheel thread and similar sized thread with lock ring thread on the other side, these do not work with small freewheels.