Simply Auto K152611 Black Polyurethane Sealant and Adhesive 310mlA rigid adhesive on a moving joint has a limited life. Panels flex, chassis twist, and anything bonded with a hard-setting product eventually cracks at the edge of the bead. Polyurethane behaves differently: it cures to a tough rubber that grips like an adhesive but flexes like a sealant, which is why it is the standard choice for panel work and seams.Simply Auto Black Polyurethane works as both a PU glue and a sealant, bonding to most primed surfaces including aluminium, steel, timber and common plastics. Once cured it holds permanently and stays elastic, absorbing the vibration and thermal movement that would work a rigid product loose.Three jobs account for most of what this gets used for. Seam sealing, where a flexible bead keeps water out of a panel joint that moves. Panel bonding, where the elasticity that would weaken a rigid adhesive is exactly what stops the bond cracking. And caravan and motorhome work, where black PU is the standard for bonding and sealing body panels, roof fittings and trim.The service range runs from -40°C to +80°C. That covers a cold night on the drive and the warmth of an engine bay or a sun-baked roof panel without the bond softening or going brittle.It can be overpainted once fully cured, which matters on visible work. A seam or a bonded bracket can be finished flush and painted over, rather than leaving a black line across the panel.The nozzle cuts down to suit the job, giving a fine bead for detail work or a wider one for filling a seam quickly. Supplied as a 310ml cartridge for a standard caulking gun.Also suitable for guttering and flashing, sealing around lamp units, metal and timber joints in the workshop, and general construction work where a joint is expected to move.Surfaces should be clean, dry and free of loose material before application. Curing takes place through contact with atmospheric moisture, so allow the bead to skin and cure fully before painting or loading the joint.