These stones have been increasing in popularity over recent years. Able to be used on hard or soft mould and die steels, OT stones are made from white premium grade Aluminium Oxide, in a medium/hard bond, which is soaked in oil during the manufacturing process. This enables the stones to be used, if required, without lubrication. OT stones maintain good shape during use, and are excellent for processing machined or even EDM surfaces. Good for use in profiling machines.