Soory wayne I don't know. All I can find is this
Poorboys Clay Bar
Poorboys Clay Bar is safe for use on all painted and glass surfaces. Its coarse-grained texture makes it highly effective at removing firmly bonded surface contaminants such as tar spots, brake dust, industrial fallout and baked-on bug remains, leaving perfectly smooth surfaces behind. Its high abrasive strength makes it ideal for the most demanding decontamination duties, but can lead to minor marring of the finish even when used carefully. Therefore, we recommend that this clay is only used when a subsequent machine polishing step is planned. For best results, it is best used in conjunction with Poorboys Spray & Wipe, although other suitable lubricants such as Meguiars Quik Detailer and Blackfire Clay Lubricant may also be used.