I used to own the FT-3 tonearm, and based solely on memory (which is a little faulty these days), I think the tonearm mass was about 10 grams. You might want to look at the web site called "The Vinyl Engine", which has a long list of downloadable users' manuals for tonearms, turntables, etc. You have to join the web site, but I think it's free. The site does have the owner's manual for the FT-3 available. Here's the link:
http://www.nakedresource.com/library_tonearms.shtml
http://www.nakedresource.com/library_tonearms.shtml