Increased bore size means greater air capacity and volume for propelling the BB forward. This is a highly recommended upgrade for AEGs with lengthened barrels since you will need additional volume of air to propel the BB out of the longer barrel - to avoid back-pressure. These bore-up cylinders actually have the same external dimensions as a stock cylinder so they will fit into a standard gearbox.
Remember to get some silicone cylinder grease to lubricate the walls of the cylinder and piston O-ring to ensure smooth operation. Find a vial in our ACCESSORIES - MISCELLANEOUS section.