The description of a spaceship or puffer in terms of its wing length, with 'x-y' representing an object with one wing of length x and one of length y. The first number is the top wing and the second is the bottom wing in the orientation that objects are presented in this wiki. For objects like the sun car, which have only one wing, a single number is used. Because many spaceships and puffers have a large number of possible iterations with different wing lengths (see Iteration guides), wing notation is a convenient way of identifying a particular iteration. Below is a 2-3 robot puffer, as described in wing notation.

x = 5, y = 7, rule = s0/b2
2bo$3bo$4bo$4bo$2bo$bo$o!

x = 5, y = 7, rule = s0/b2

2bo$3bo$4bo$4bo$2bo$bo$o!