Due to the long span of labial arch wire in the “wrap-around” design, the labial wire often has a great deal of "flex." It may, as a result, come out of adjustment if the appliance is handled roughly. To help alleviate this problem -- and add stability and retention to the anteriors -- clear acrylic is processed tightly against the labial surface of the incisors. This feature adds superior retention to the overall appliance, eliminating the need for a small interproximal support wire distal to the lateral incisors (as seen in the San Antonio design).