A non-porous, multi-purpose spa surface cleaner, Multi-Surface Care does not contain harsh acids. This has been specially formulated to remove body oils, grease and dirt that form the so-called "bathtub ring" on spa walls. Also for use on spa hard covers to help remove dirt and oils.  Just spray on surfaces and wipe off with damp sponge or cloth or apply directly to the sponge for wiping up surfaces. Splash water on the cleaned area to remove residual material.