RV Designer Bubble Level Screw On 2 1/2in x 1 3/4". Use the bubble as a leveling guide. When the bubble is perfectly centered between the two lines that means the surface is level. If the bubble is closer to one line than the other then the surface is not level. The E409 Bubble Level features a screw-on application. The dimensions of this level are 2-1/2" by 1-3/4". Each package includes two screw-on levels and mounting screws. Features of RV Designer E409 Bubble Level Screw On 2 1/2in x 1 3/4" Ensures surfaces are evenly horizontal or vertical Screw-on application Use the bubble as a leveling guide When the bubble is perfectly centered between the two lines that means the surface is level Dimensions: 2-1/2" x 3/4" Package Contents: RV Designer E409 Bubble Level Screw On 2 1/2in x 1 3/4" RV Designer E409: Bubble Level Screw On 2 1/2in x 1 3/4"