weights on Sumiko MDC800 versus MMT,FT3

Avs9, The MDC 800 was sold with a particular counter weight
depending from the customers cart weight. But there are 5 counter
weights for this tonearm marked with letters: l,m,h,x and a. With L for 6 g.(+/-2), M for 8g.(+-2g.) ,H for 10 g.(+/-2g.), K for 15 g. (+/-2 g.)and A for 18 g. (+/-2 g.).
All those weights share one common decoupler which need to be installed 'in' the weights with the help of a tool called 'wrench'. So you can use your H weight for the carts from 10- 12 g. weight. That is to say with the optimal position of the weight in (co)realtion to the pivot. I am, alas, not familiar with the MMT/ FRT3/FT4 versions but
if their rear armtube is of the same thicknes as by MDC 800 you can of course try.

Regards,

Addition, Sorry Avs9. I made a typo. You can use your H weight for the carts from 8 g.- 12 g. weight.

Regards,

Thank you, Nandric, the arm on MDC800 is 10.5 mm as my micrometer shows, the answer about that I got from someone selling FT3 on ebay was 'about 12-13 mm'. On the good side it is not less, but it doesn't look like they are interchangable as is.
Regards