High grade original Tannoy type APGS15N FERRO FLUID 0.6ml in syringe.
High grade original Tannoy FERRO FLUID, type APGS15N, approx 0.6ml in syringe, from the original suppliers to Tannoy. Tannoy used to issue one with their tweeters and send 0.15ml which was more than plenty for one, so 0.6ml should be enough for 4+ small tweeters, 2+ large tweeters.
Exact volume is min 0.5ml, but usually you get 0.6ml.
Be aware, much of the Ferro Fluid on the internet is poor quality stuff from China !! Not ours.