Simpson Monster 150-Foot (3/8") 4500 PSI High-Pressure Hose w/ Quick Connectors

Regarding non-marking leaving “marks” the non-marking hose jacket is a silicone rubber compound. When being used it does not permanently mark or staining the surface.

However all hoses, standard and non-marking blue and gray, when being dragged across a rough surface have small particles of the rubber outer cover abraded off. With non-marking hose there is no carbon black in the jacket material that stains or permanently marks the surface. The small particles of rubber jacket however will show and can collect in depressions on the surface or where rinse water is channeled by the hose itself or other equipment. These particles are easily rinsed away. High temperature operation softens the silicone rubber jacket material and causes the hose to abrade easier leaving more jacket material on the surface.

Standard black pressure washer hose is a different rubber compound that contains carbon black. When black hose is exposed to water, high temperatures and many common pressure washer chemicals the carbon black will leach out of the rubber jacket and permanently stain the surface.