On the bottom of the mouse you will find a single push button release that will open the pop-out tray where the weights can be installed inside the Sidewinder.  We used the Sidewinder with various weight setting trying to find what we considered our optimum weight setting.  What we ended up with was 15 grams.  Any more than this and the it felt like the mouse was working against me.

Here you can see the aluminum roller wheel and behind it the three settings for adjusting the DPI of the Sidewinder.  The button located on the side of the mouse directly in front of the two metal buttons is the used to to record macros.

The base of the Sidewinder has a total of five replaceable feet, the feet can be removed simply by placing a fingernail under the edge and lifting it up.  To replace the feet just reverse the operation.  It should be noted that each of the three sets of mouse feet offer a varying degree of resistance.  For example if you keep mousing past your target in game it would make sense to either drop the DPI setting on the mouse or install the mouse feet that will add more resistance to you mouse during game play.  Now you can see the rectangular button that opens the side compartment on the Sidewinder.

Another clever device that comes with the Sidewinder Mouse is the black non-descript box that holds all of the weights and the extra set of feet for the mouse.  When I  say this item is clever I am not referring to the fact that it is a box, but instead what the second duty of this box is.