Get an instant reading on APS water levels – and visual assurance that your seedlings aren't going thirsty. Just slip this gauge into any size APS, and the red float will display the exact depth of the water in the reservoir. Indicator is red and is easily seen through the clear plastic. The higher the red pin, the higher the water level. If you can't see the red pin, it is time to fill the reservoir! Overall, approx 4 1/2 inches H x 3/4 inches W Clear top with red tip, brown bottom Weighs 1/3 ounce