A method of formulating a latex ink composition for a specific application temperature can include the steps of determining an application temperature for the latex ink composition; choosing at least one polar monomer having a dielectric constant of at least about 3. The bottom-end side of the water motor has a guide groove with a restrictive hole for the extension of a switch shaft there-through. Thus, the characters are not superimposed on the image, and they are easy to see. A sensor is mounted in the chamber. The flexible circuit connection interface may be connected to an external interface. In a third embodiment, the rocker is surrounded by a box, which together with the rocker can be removed from the weapon, in a similar manner to the interchangeable magazine.