Franklin Fueling FEB-125-M 4” Electrofusion Fiberglass Entry Boot is for use with UPP® brand secondary contained pipework systems. It’s suitable for use on single wall containment sumps with wall thicknesses that do not exceed maximum thread width of each entry seal (This entry boot is not recommended for double wall or curved sump surfaces). It also allows for electrofusion welding of secondary contained pipework directly to boot.