yup it's for BT auto. s/steel 1.5" diameter... length not sure need to refer back to JianHang, but looks closed to HKS Jasma 4-2-1. feel an increase in mid and top-end.
still need to complement it by putting thermal wrap and redo the piping again coz my bullet is 1.7" but the piping is 2.2".
got it after 2 weeks @ RM6++ include installation. 3rd or 4th time going there, starting while using the old 4AFE. like the workmanship.
actual intention is to customize the length but then thru my research, I couldn't suitable info on it. i refer to sifu Acoustic website
HOME - CHIN Fa Cheng's Technical Website for Acoustics, Audio and Car. anyway Mr.Chan of JianHang said he will assist in finding the best length.