Effective mass of 3.5-4 grams without headshell makes absolutely no sense to me on this arm but I could be wrong.
If I am not mistaken, Jelco makes these arms for Ortofon and the 9" version of the arm most closely resembling the 309S with Jelco's stock headshell (12 grams) is 20 grams. Add another 3" of arm tube and I cannot see how this arm would not have an effective mass with the stock Jelco headshell of much less than 23-24 grams and even more with the SPU headshell.
As I say, I could be wrong.
If I am not mistaken, Jelco makes these arms for Ortofon and the 9" version of the arm most closely resembling the 309S with Jelco's stock headshell (12 grams) is 20 grams. Add another 3" of arm tube and I cannot see how this arm would not have an effective mass with the stock Jelco headshell of much less than 23-24 grams and even more with the SPU headshell.
As I say, I could be wrong.