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