i wanted those for my helicon so i asked thoman about dimenssions...this it the email i recieved:
thank you for your message:
The interior range is by the
part 1 : 12,2 mm - 14,8 mm
part 2: 12,8 mm - 14,6 mm
- interior length of straight part of tuning bit in milimeters is 42 mm by both bits.
The bits fit and are tight and solid...get them if you need to acomodate muthpiece position