This is a heavier-weight spring for certain Futaba transmitter gimbals. For the modeler who wants a stiffer 'snappier' feel to the radio's response. ** DO NOT USE THESE IN THE 14MZ, 12Z, 18SZ or 18MZ AS THEY ARE TOO HEAVY ** ** CONTACT FUTABA SERVICE CENTER TO ORDER THE ONES MADE FOR THESE TX'S** FITS: Fits SOME airplane Futaba series transmitters 4/10/01 amc COMMENTS: Modification of your transmitter in any manner voids the transmitter' warranty. For spring installation into a transmitter while under warranty, please send the radio to the Futaba Service Center. If Futaba is not performing the installation for you, Futaba can not guarantee the workmanship of the installation. Therefore, Futaba is not liable in any manner for any damage done to the transmitter as a result of the installation of these springs.