Pelsue Manhole Shields are temporary Pneumatic seals that keep ground water from flowing into the open manholes. Just inflate tube with 5-10 lbs. of air or nitrogen to form a water-tight seal. No clamps or sealing compounds required. Series 2730 (reversible 27" & 30") fits most communications manhole openings. Model 3336 (33" & 36") fits many Electric Utility manholes. Custom sizes are available. All aluminum fabrication.