Ironman 4x4 Polyurethane Bushes feature a unique high density injection moulded polyurethane material, providing precise location and a durable bearing surface for your leaf springs, making them very durable in hot temperatures whilst providing soft comfortable vehicle ride. All Ironman spring bushes also feature the special spiral and flange grooves - incorporated grooves and spiral bore rifel - to distribute lubricating grease evenly throughout the bushing surface when combined with greasable shackles and pins.Ê