The Efreet Custom is a modified version of one of the eight MS-08TX Efreets that were manufactured, and is equipped with the EXAM System. The Efreet was chosen as the base unit because no other machines could withstand the EXAM System. Compared to the original Efreet, the Efreet Custom has a larger head unit without Vulcan guns, and this was to accommodate the first EXAM System and its associated cooling units. The mobile suit also has improved mobility due to a reduction in weight and more powerful thrusters, as well as higher offensive power, making it more powerful than the original Efreet. Additionally, its close combat capabilities surpassed that of the MS-07 Gouf.
When the EXAM System is activated, Efreet Custom's already high levels of performance and mobility are boosted even further, allowing it to match newer mobile suits. However, it quickly overheats when using this system and to overcome this issue, the mobile suit's cooling system are enhanced. Spare parts are also hard to procure for this mobile suit due to the low production number of the Efreets. Parts from the Gouf series, which has a close lineage, could be used, but they are still subjected to the severe wear and tear caused by the EXAM System. Despite having excellent performance, it was said that the Efreet Custom failed to meet the expectations of its developer, Chlust Moses, who then defected to the Earth Federation in order to develop a higher performance machine.