the cheaper supplier is lakehurstpt
http://www.lakehurstpt.co.uk/lakehurstpt_update_147.htm
The website is bad but they gave me these details in an email
'Yes, these racks can be used in CNC applications depending on the application requirements (The quality Grade of the toothing is from 8 to 9 at Din 3962/63/67) you should research these Standards before placing you order to ensure they will be suitable for your application drive requirements?'
other suppliers i.e cnc4you,cncrouterparts don't really give much info at all