Official O2 Classic Pay As You Go SIM Card – UK - Credit rolls over - 3 in 1 SIM
3 in 1 SIM gives the option for Micro, Nano or Standard Sim size. 1 x O2 SIMCARD(3in1 SIM gives Nano/Micro/Standard option). Just ensure to make a chargable call or text in a 6 month rolling period to keep the SIM active with O2.