biological grinding spheres???

[MDELAVINA at IRRI.CGNET.COM]

Howdy Everyone!!

I just would like to ask where can we get some specifications about 
biological grinding spheres?  I just read about it in an article so I 
haven't seen one.  I guess it's spherical. From the article, leaf tissue can 
be homogenized by simply placing the tissue in a 50 ml tube, then these 
spheres, then pouring in liquid nitrogen and then vortexing it for a full 
minute. 

Any leads that you can give will be very much appreciated.

Mercedes C. dela Vina
Junior Research Assistant
Molecular Plant Pathology Lab
International Rice Research Institute
Los Banos, Philippines