When you design your project and you select a grate design, it is often necessary to consider slot size.

We have identified the USF grates with relatively small slot lengths as "Restricted Grate Openings". this term is applied when the slot lengths are 6-1/2 inches or less. 

The 6-1/2 inch dimension is an arbitrary length and does not imply the recommendation of a grate for any particular application.