2007 KTM 990 Adventure Fuel Pump O-ring Sizes Smaller o-ring (radial seal): 60 mm x 3 mm buna-n Larger o-ring (face seal): 65 mm x 3 mm buna-n I just about finished painting and re-assembling my 990 (long story) but I sliced the radial seal o-ring on the fuel pump while trying to re-install it. I read a bunch of stuff and found out that rather than pay $50 for 2 KTM OEM o-rings, people have found McMaster-Carr substitutes. Unfortunately, I had already ordered and paid for the OEM's before finding the McMaster-Carr substitutions. I supposed I could have measured the grooves and guessed at the right size but I didn't (just wanted to get back on the trails ASAP). Fortunately, I decided to measure them before installing. While many have used a size 932 o-ring to replace the radial static seal (most people re-use the face seal o-ring), the actual size is 60 mm ID x 3 mm cross section diameter. This is only slightly different than the 932 but I believe it's the correct size. I've also seen size 229 (I think) used but this has a 3.5 mm cross section diameter and, although slightly smaller than the 60 mm, it has much more volume (total material) to squeeze into the o-ring groove, which is about 2.5 mm deep and 3.5 mm wide. That said, it has been used successfully. Note that the hole in the tank is about 65 mm in diameter. The face seal o-ring is 65 mm ID x 3 mm cross section. I've read that size 230 has been used here successfully. Although it has much more volume than the 65 mm one, I guess it works because it's a simple face seal and the groove is about 4 mm wide, providing plenty of space for the o-ring. Also, Viton is not necessary. The buna-n material works just fine with gasoline and ethanol. That said, since the buna-n o-rings come 100 to a package for $14.95 and you can get 5 Viton o-rings for half that, most people go with the Viton. Lastly, I've read and experienced the difficulty in getting that fuel pump back in the hole without shearing off the radial seal o-ring but someone said they did it by using the 4 screws to pull the pump in evenly. This works great. I also put a little oil (vacuum pump oil - mineral oil) on the seal and the hole before installation just ion case (just a film). This is a very good technique.