ALTANA Gardner-Scrub Manual - Manual (Page 14)

Up to three brushes may be run at the same
time.
Additional weights of 500 and 1000 grams
are available to put extra pressure on the
brush to speed failures on tough coatings.
However, these weights fall outside of the
ASTM specifications. The weight slides onto
the pins of the brush holder.
NOTE: Additional weights may not be
compatible with all brushes, test your brush
with extra weight before committing to a
change in your test specifications.