The CFA300X is a slim (OD 40.6mm) 3-axis FOG AHRS system designed specifically for horizontal drilling applications (HDD). The system is designed to be mounted in the bottom hole assembly (BHA). After initial alignment, the CFA300X enters continuous navigation mode (AHRS) and provides continuous updates of azimuth and attitude when requested via the client-server RS485 interface. If necessary, gyrocompassing can be performed at anytime. The design has been proven reliable with many thousands of field hours in extreme conditions.