MA-505xl? Is that the 12 inch version? I don't know what its effective mass is but it is a heavy arm. I used to own a 505s which was a 9 inch arm with silver wire. When I was making the purchasing decision, I was debating whether to get the 9" or the 12". I remember I auditioned the 12" arm with an EMT cart tracking at 3g! It is a heavy arm. Don't try anything with high compliance on it.
