Designed by RIVA Racing's Development Team this new pump impeller for our 2018+ RXT/GTX 300 Stage 2 Kit produces an additional 2~3mph top speed and +150rpm. This new 159mm pump impeller is an exclusive "R" model and requires installing a smaller 159mm wear ring. This new pump combination is an easy-to-install and cost-effective upgrade for our 2018+ RXT/GTX 300 Stage 2 Kit that will satisfy those looking for more top end speed (+2~3mph) and don’t mind sacrificing some initial acceleration performance (compared to 161mm Solas SXX-CD-13/18).