VHM make a range of inserts to which they have tried and tested which the part number 

is AE32----- then a Letter ie AE32056-E, if you wish to have a insert of another design the part number would end in a number rather than a letter. i insert coded with a A in all cases will have been sold as i un cut insert with no combustion chamber design and as such would not in future be recorded at VHM