The circuit above is actually a multivibrator, i.e. a free-running miltivibrator. It's identical to a flip-flop that triggers itself repeatedly. Q1 and Q2 are general purpose PNP transistors (2N3906, 2N2907, etc). R1 and R2 limit the current to the LEDs (which flash alternately). Increasing the values of C1 and C2 will slow the flash rate.