Stihl makes a surprising variety of engine sizes. There is no substitute for cubic inches however the numbers are in cc.

Weedeater
27.2cc

Brushcutters
25.4, 31.4, 30.8, 36.3, 40.2

Clearing Saws
30.8, 36.3, 40.2, 44.3, 48.7, 51.7, 56.5

Backpack Blowers
27.2, 44.9, 56.5, 64.8

There are more sizes.

Does anyone know if Ryobi makes engine sizes larger than 31cc?

Bill S