The FRSKY X18S is a highly sought after radio since it was only made for a short period, it was discontinued to make room for the X18SE. There are only a couple of these left brand new in the world. 
 
When you are investing in a new radio and considering what requirements are important to you, if weight and comfort are primary considerations, followed by the benefit of the excellent system features of ETHOS, then the FrSky Tandem X18 series radios are obvious appropriate choices.
 
The Tandem X18 series dual-band telemetry radios benefit from an enhanced ergonomic design with rounded and more comfortable hand grips, along with an improved case design to make the radio fully stable when standing. The radio includes easy-to-reach sliders and switches, 4 standard stick trims with additional 2 extra trims added to provide more flexibility with flight attitude adjustments while operating the radio. The X18 series include further enhancements with integrated flash storage which improves and simplifies storage operation and use, and the interior of the radio has been designed with space and weight in mind, while still keeping all ETHOS setting and control features for the pilot to enjoy.
 
Internal 900MHz/2.4GHz Dual-Band & External Module Bay
The TD dual-band RF system combines both the features and advantages of FrSky 900MHz and 2.4GHz RF together in one system. The TD features real simultaneous dual-band longrange control with telemetry that achieves reliable end-to-end 4ms latency while maintaining a robust and high-quality signal link. The entire range of TD, ACCESS & ACCST D16 receivers are supported. The built-in TANDEM RF System supports ACCESS and ACCST D16 protocols.

In addition, the Tandem X18 series radios include a rear Lite version module bay to offer more options to connect external devices. FrSky welcomes working compatibility with the 3rd party products with their own developed technology following FrSky verified 3rd party compatibility-testing program.