This weir attaches to the BioSteps 10 discharge outlet to make the filter into a filter falls. The waterfall does not come with any plumbing or fittings. The necessary plumbing is included with the BioSteps 10 filter.
The waterfall weir portion of the attachment is 11-1/4 inches wide. See the image below for all the dimensions.
Waterfall attached to the BioSteps 10 filter (not included).