Very many gap-sealing products are now available for use in the compressor section of gas turbines. This paper attempts to give an overview of these and where they are best used. Data is presented for abradability, erosion resistance and application technique. By explaining how abradables function tribologically it is hoped that selection will be simpler for designers. New products are introduced as well as the way forward described. It is shown how with time the diversity of application techniques has decreased with thermal spraying becoming the preferred technique, and that abradables are now available to run against titanium blading up to 600°C.