It was either flephedrone (4-FMC) or 3-FMC. Either way, if you're in the UK or anyplace else that placed a general ban on cathinone derivitives, it's illegal.
Also, IMO, it's ridiculously overrated. Both 3 and 4 FMC were very dissapointing (for me at least) - dirty stimulants with little to offer other than palpitations.