Risers eliminate the need to dig up the septic tank lids for servicing by extending the lid up to ground level. This kit includes all materials needed to install a septic tank riser up to 18" in height. Included in this kit: 24" Dia x 18" of dual wall corrugated riser material, 24" Seal R Adapter Ring, 24" Polylok Riser Lid, and (1) can of spray foam. This kit will accomodate a tank opening up to 33.5 inches in diameter.