Those are flash board riser systems. AgriDrain makes them with seals and those work pretty durn good. https://www.agridrain.com/shop/c8/structures-valves-gates/


www.hoosierpondpros.com


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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).