The IS20 number are wrong the turbine is 51mm inducer 42mm exducer ( 41.8mm). 47mm exducer does not make sense with 51 inducer.
I guess this number come from those number posted by Arin from APR for Golf MK5, MK6, MK7 where their is a lot of mistake's
like also the K04-064 compressor wheel is...