(Reposted Due to Typo in Numbering). Once in an aircraft, each set will corrispond to its designated speed, or around that. These units can be placed anywhere on a your plane, and a red light comes on when you are below the designated speed (35, 50, 70, 90, or 260) to alert you that you are reaching an unsafe speed. Both of these units are the same, they just are different shapes. Place it by using the little blue pylon it comes with (recommended), or by placing it with the outside box or cylinder of the unit. (WHEN PLACING MAKE SURE YOU DO NOT CONNECT ANYTHING ON THE INSIDE OF THE UNIT TO YOUR CRAFT)Once again, this is non-modded and purely mechanical.