Size of the RC engine usually relates to the model it is intended for, as follows
.05 to .09 for 1/16 scale
.12 to .18 for 1/10 scale
.21 & upwards for 1/8 scale nitro models.
Petrol models usually have 23cc to 28cc 2-stroke engines fitted
(Click on picture or link for more info on our RC Engines)