Abstract: A mark retaining structure of a micro-differential pressure gauge includes a mark member attached to the edge of the micro-differential pressure gauge for indicating the critical value. The mark member includes an engaging portion, an extension board and a hook to engage with a recess and a circular flange of the micro-differential pressure gauge. The present invention provides a positioning function.

Abstract: A fuel level indicator for a portable fuel tank comprises a base, a platform hingedly connected to the base, a biasing member between the base and the platform to bias one end of the platform away from the base, and a visual indicator. When the fuel level indicator is positioned under one edge of a full portable fuel tank, the platform pivots to a first position where the visual indicator indicates a full tank, and as fuel is withdrawn from the tank, the platform pivots toward a second position where the visual indicator indicates a less than full tank.