1 1/4 in. nylon insert adapters are used to adapt female pipe threads to poly pipe in a straight line. These fittings are for cold water applications only. These fittings can be used underground or above ground for water service and agriculture uses. They are NSF approved. Nylon insert fittings are tougher and will absorb shock better than poly insert fittings. Use stainless steel hose clamps to join fitting to pipe.