The number is critical. This was the last major firmware update Sony released before shutting down PSP support. It is the golden standard for custom firmware, supported by PRO-C2 and LME-2.3. Consequently, the library of themes for 6.60 is the largest ever created.
Gritty, dark themes featuring Kratos and metallic, blood-stained icons. Psp Ctf Theme Pack 6.60