Phase 7 is an area on SR388. It is the seventh explored area in Metroid II: Return of Samus, and is very large in size. All four beams are available here, due to the fact that they cannot all be used at once. However, if Samus Aran wants to use a certain beam at a certain time, she can simply reobtain it from the same location.
Complete Map of Phase 7: 
|Areas of SR388|
|Phase 1 | Phase 2 | Phase 3 | Phase 4 | Phase 5 | Phase 6 | Phase 7 | Phase 8 | Phase 9|