effective mass of Jelco tonearms

I have e-mails directly from Jelco stating that the effective mass of the 250 is 18 grams and the 750D is 20 grams, including headshell. They did not say anything about the effective mass including a cartridge. The e-mails are from 2009 and 2010.
-Bob

The effective mass including the cartridge will vary with the weight of the cartridge.

Put a nude Denon 103r in a shaved-down lightweight wooden shell and that doesn't weigh much. OTOH, some of the larger boat anchor cartridges even need an extra heavy counterweight just to balance the tonearm.

My Denon DL-130R balances just fine with my 750D. And I think is a perfect match compliance wise. I plan on rebodying the 103R with a aluminum body some day. That's when the heavier counter weight will come into play...