I also made MW elements with 6.5mm.
But MWs are rare over here and the number of people asking for MW was poor.
On top the MW elements are made of used 5.5mm with a new plunger and matched into the cylinder.
Way more machine hours resulted in 75 EUR/element.
The last set I sold in November but the buyer gave it back as his shop told him that the elements were used...
If you want big MW elements follow he 10mm threat or contact OM616 member.

Tom