I have always used 85 grain thunderheads on my carbon arrows. I bought the new and improved thunderhead 85grn. With the new broadheads they also tell you to use a U.B.A.R ring when using carbon or smaller dia shaft. UsuallyIjust used the locking ring and the rubber o-ring, has always worked fine before. Now they say locking ring then rubber o-ring then u.b.a.r ring. I put it on without the u.b.a.r washer and it fits like the old ones....blades are tight and secure.Never had thiswasher on any others I have bought in the last 6 years. Can't tell any size difference from the old ones, just the micro grooved ferrule is all. Didn't know if anyone can tell me if these u.b.a.r washers have to be on or not?
Thanks guys!
crutch

Use the UBAR if you're using Thunderheads on carbons. If you don't the blades can come off when shot into a critter or target. USE THEM. I used 125 Thunderheads for more than a decade. This year I switched to the Shuttle T. They're such great shooters and do some damage. I always loved my Thunderheads butI like these Shuttle T's a lot.

I think the reason they want you to use the UBAR is with the smaller diamter arrow the o-ring might slide up onto the shaft, and without having a metal insert to push agains the carbon could cause alot of wear on the o-ring. I used them on my easton axis arrows last year, it also makes for a cleaner flusher fit from the arrow to the broadhead.

I use the UBAR's the o ring gets all funky if I don't

Thanks guys! Like I mentioned I have been shooting them like that for six years without a problem. I thought maybe they did something to the broadhead that required them.

Is the washer calculated into the 85 grn? Maybe they removedenough material with the new grooves in the ferrule and that makes up the diffin the ubar washer?

Thanks again!

The washers weigh like a grain, they are next to nothing. No difference in shooting.