How big is this gear?
The size of any gear or ring or hoop can be reasonably approximated. To find the diameter of any circular gear divide the tooth count by 10 for a diameter in centimeters or by 25 for a diameter in inches. This will give a reasonable approximation of any Wild Gears gear diameter.
How big a design can I make in this ring?
The maximum design size that can be made in a ring is about 10 mm less than the diameter of the ring.
This is because the pen hole that is closest to the edge of any gear is inset by 4mm; and most pens put the line near the middle of the pen hole (3 mm diameter) not at the very edge. So that gives about a 5 millimeter inset from the edge of the gear, measured from the tip of the tooth. Count that twice, once for each side of the design to get the diameter offset.
This is because the pen hole that is closest to the edge of any gear is inset by 4mm; and most pens put the line near the middle of the pen hole (3 mm diameter) not at the very edge. So that gives about a 5 millimeter inset from the edge of the gear, measured from the tip of the tooth. Count that twice, once for each side of the design to get the diameter offset.