Cut back blades means the turbine impellor blades are trimmed back (usually bu 30 degrees). This gives more lag, but enables more power at top end. Turbo thrust bearings are normally 270 degrees, specially machined ones are 360 degrees.

Cut back blades on that turbo are a no no on RST, it'll be too laggy, and the exhuast housing is a little big too - better with a 0.48.