The illustrations show a Patek balance wheel, know by the trade name "Gyromax." The Gyromax is constructed of
Glucydur. Eight small weights, slipped over posts are set down into the balance wheel rim as illustrated
above. The weights may be rotated on their posts in opposing pairs to adjust the rate of the watch, or individually to adjust the poise
("balance") of the wheel. The weights are sometimes also used in positional adjustment of the watch.
As shown left, the circular weights contain a slot, which is the "light point" of the weight. If
the weight is turned so that the slot is closer to the outside of the balance (away from the center), the mass of the balance is moved towards the center. This speeds up the rate of the watch (opposing pairs of
weights moved equally) or decreases the effective mass of the balance at that point (only one weight turned). Conversely, rotating a weight so that the slot is closer to the center decreases rate or increases the
effective mass at that point of the rim.