Grips

Overgrips, replacement grips and towel grips.

Worth being clear on the difference. A replacement grip is the base layer that goes directly onto the handle. An overgrip is the thin wrap that goes over it, costs little, and is meant to be changed often - every few sessions if you sweat heavily. A towel grip is cotton towelling, absorbs far more, and is popular in Malaysian humidity; it needs replacing more frequently because it holds moisture.

Each layer adds a little thickness, which effectively moves your grip size up. If your racket came in G5 and you run two overgrips, you are playing something closer to G4.