The soprano is the smallest member of the sax family and is pitched in Bb.  Usually these are straight instruments without a curved bell, but some manufacturers also produce a curved version which looks similar to the alto.  The straight soprano sometimes comes with two necks, a straight and a curved one. 

  When standing to perform, some players find it easier to use the straight neck, whereas when seated it can be more comfortable to use the curved neck, as the finger positions remain the same, and the angle of the mouthpiece doesn't alter.