The JEM-X instrument utilizes two identical, high pressure, imaging Micro Strip Gas Chambers (MSGC's) as detector units. The primary energy range of the detector is 3-35 keV. The design is based on the heritage of DSRI's HEPC/LEPC instruments onboard the Spectrum-X-Gamma satellite. The main differences are the larger active area of 500 cm² and 5 bar Xe/CH4 gas filling instead of 150 cm² and 1 bar. Microstrips are patterned on an octagonal shaped glass substrate. One coordinate is determined by the cathode strips, while the other coordinate is measured from the induced charge distribution on the backside strips. The active area is equal to the window diameter of 250 mm. The active area on the backside is surrounded by a veto-ring. The 250 µm thick Be window is supported by a collimator made of Mo lamellae coated with graded shielding materials.