"It lets you know at a glance when the grain tank is full so you catch it before it over-flows," says Delmar Martin, Delavan, Ill., about his new "Sight Gauge" for Deere 6620, 7720 and 8820 combines.

"Usually on these machines you have to open the door, lean out and look up to see if the tank is full. Or, if you have an electric bin-full system, there's always the danger that the components will fail or wear out. This gauge has no moving parts and will never wear out," says Martin.

The gauge consists simply of a metal housing that covers a small portion of the glass window in the grain tank and keeps grain away until it rises high enough to enter a short length of 2-in. PVC pipe that extends up to just under the overflow level of grain in the tank. When grain rises to the top of the pipe, it falls down into the pipe and into the sight gauge. When the tank empties, the gauge also empties out.

To install you remove one existing bolt by the air filter in the grain tank and slip the upper lip of the gauge under the combine bin lip and replace the bolt with a longer one. Height of the PVC pipe is adjusted by loosening a clamp.

Martin says he's willing to work with farmers to adapt the sight gauge to other combine makes as well.