This set includes 1pc 12mm and 1pc 24mm, which can be used separately or stackable together to better control the minimum focaled length of the lens Supports electronic communication between the body and lens, thus maintaining the convenience and picture stability of autofocus and auto exposure functions This electronic autofocus adapter rings, automatic extension tube for z port lens, providing a practical solution for macro performances The extension tube not contain any optical components, so the picture of the lens will not decrease Lightweight, the metal stand provide additional durability and can bear switching between the lens and other tubes for long time use