An unmanned mobile suit stationed on the Moon to protect D.O.M.E., the main weapon of the G-Bit D.O.M.E is the Satellite Cannon, which has a different design from that of the FX-9900 GX-Bit.
The cannon fires small bursts of energy and it has not been shown whether they can produce a powerful energy beam like the GX-Bits using the satellite system. Also unlike the GX-Bit, the G-Bit D.O.M.E only has two reflector panels on its back instead of four. Apart from the satellite cannon, the Bit is also equipped with a chest-mounted beam machine cannon. [Source: wikia]
You can download this papercraft template here: SD GX-9900-D G-Bit D.O.M.E Free Gundam Papercraft Download [Instruction]