During the development of the WP AER 48, WP benchmarked the AER system with conventional systems, which use spiral springs. Both systems showed different advantages, which were each favored by different riders. In order to provide both options, WP has decided to also provide a retrofitting kit, which simply allows rebuilding the AER 48 technology into a conventional system. With this kit, the AER 48 air cartridge on the air fork leg is replaced with a spring cartridge kit. All functionalities remain at the same level, with the feeling and functionality of the conventional system. The damping side remains unchanged.