MacCready Ring, 57 mm, unmarked, with bezel-ring
The MacCready type ring is an indispensable aid in cross-country soaring.  The ring is rotatable and is marked with speeds and a white triangle.  The chief use of the MacCready ring is to achieve the highest possible cruising speed (average cross-country flying speed) on thermal cross-country flights.  This involves setting the white arrow to the anticipated rate of climb for the next thermal.  Optimum flight performance is assured when the airspeed indicated by the airspeed indicator corresponds to the preselected flying speed to which the MacCready ring has been set.  The MacCready ring allows gliding distance and final approach  to be optimized.  Please refer to relevant literature for further details.  When ordering, please do not forget to state the type of aircraft in which the ring will be used.  If the ring is retrofitted to a variometer of older design, the original threaded ring of the instrument must be removed and replaced by a grooved threaded ring onto which the MacCready ring can be fixed with ease.
Variometer not included.