The Longines 998.2 is an open face calibre watch movement featuring a Breguet hairspring. Designed specifically for the US market, it incorporates a negative stem mechanism. The movements share the same layouts for the base plate and bridges but exhibit varying heights and stem mechanisms, with one version having a larger diameter suitable for US cases. They are typically signed with the diameter in lignes and height in 1/12 lignes or a newer 3-digit designation. The Longines 998.2 movement includes the functions of stem winding and setting, as well as a sub-second display.