Definition: An RC may have two different types of foam insert. Some RC tires have removable foam tire inserts that fit inside the tires and help them keep their shape. The air filter on a nitro RC has a foam insert that catches dirt and debris.
The foam insert in an RC tire can be changed out for softer or more firm foam to improve traction on different surfaces. The foam insert on an air filter must be cleaned and oiled regularly.
Also Known As: insert | inner foams (for tires)