When I put them on my axles, I read on Pirate that the F-Toy guys were cutting 1" size slits in between one of the bellows. I did this to mine when I put them on, but after one season, my front inner seals were blown. I rebuilt the axle, and actually cut another 1" size slit on the opposite side of the first cut on both front and rear. I am not sure if this fixed the issue or not, as I haven't back into my front axle. I haven't ever had an issue with the rear, except one time coming out of HTT on that long backroad. The diff got warm, and pushed oil past the rear seals. I thought they were blown, so I went and picked up two more seals. But they never leaked again after. On the rebuild, I think I am going to run a long hose and filter. As much as I like the idea of them, unless I find a better way to get them to breathe, its not worth blowing the seals. On a side note, the buggy was upside down for probably 20 minutes at one of the comps last year, and I never had any oil sneak out of the cuts.