CLR=Calcium,Lime,Rust removerJK47;2278873; said:CLR is a calcium and lime remover. I believe that is what the letters stand for anyway. Just MAKE SURE you use the GREY bottle. It was suggested to me by one of the other members of this site. Worked great for me. Just rinse, rinse, rinse then do rinse it again to make sure there are no trace elements left when you are done. It is a cleaning agent after all.