From Halopedia, the Halo wiki
SRR stations come in different shapes. Some of them, such as Cradle, are essentially large rectangular plates of Titanium-A, while others, such as Anchor 9 are more complex in construction, featuring three main sections connected by beamwork and a central hull. Cradle-type stations are equipped with subluminal drive engines as well as a slipspace drive, allowing them to travel with UNSC fleets and provide repairs when needed.
One Cradle-type station is capable of refitting six destroyers, three from her upper surface and three from her lower surface, in a matter of hours. The planet Reach had 18 SRR stations orbiting it by 2552. The mobile hospital ship UNSC Hopeful was constructed from two scrapped SRR stations.
As the fortunes of war against the Covenant worsened, the UNSC began to use such stations as shields for their fleets in major battles. Four such stations were destroyed with all hands lost in the battles of Sigma Octanus IV and Reach, including the UNSC Cradle, which sacrificed itself to save the UNSC fleet at the Battle of Sigma Octanus IV from destruction.
Refit stations possess enough mass that their destruction can disperse debris widely enough to protect formations of ships from Covenant fire. This strategy of sacrifice was used effectively during the battles of Sigma Octanus IV and Reach.
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