Ty: Are you sure that the IRS axle uses the "D" type diff rings??? I was going to buy the IRS axle for my SpeedMerchant Rev.3 (even though I don't like the axle color ), but when I viewed the photo on the IRS web site http://www.teamirsrc.com/irs131.html the diff rings were standard round ones. Unless the photo is wrong, I really couldn't justify spending $45 to replace the standard Associated axle for the IRS unit. Also, I like the fact that the left diff hub on the Associate axle threads on, rather than clamping or using a grub screw.

BTW, when I had a Carpet Knife it had the "D" rings on the diff. My, Rev.3 came with an Associate axle that uses round diff rings. The thing is, when driving the car, I can't tell the difference??? What advantage do "D" rings provide?