The Pentagon (Пентагон) home computer was a clone of the British-made SinclairZX Spectrum 128. It was manufactured by amateurs in the former Soviet Union. Its PCB was copied all over the USSR, which made it the most widespread Soviet ZX Spectrum clone. Many simple devices (upgrades) were invented to connect to the Pentagon with a soldering iron.
The last Pentagon model was the Pentagon 1024SL v2.3, which included most of the upgrades of the standard Spectrum architecture, including 1024 KBRAM, Beta 128 Disk Interface and ZX-BUS slots (especially for IDE and General Sound cards). This model also featured a "turbo" mode (7 MHz instead of the original's 3.50 MHz).