My 1983 v65 Magna has a mac 4 to 1 exhaust, and the jets have never been changed, 31 years. The simple jet calculator said ultimate, I said what the heck, for the price, to it me was worth it to check it out, well the bike runs smoother now, its not as noisy now at idle. Fast shipping, nice packing material. Thank you CarbJetKits, It worked for me.