What size DonnyFL Suppressor will I need for .177

I heard that you ought buy a suppressor one size larger than your rifle's caliber.

Ok, that makes since, only I went on DonnyFL's web site, saw the calibers for their suppressors and am not sure of which one I'll need. I'll call them tomorrow, but in the meantime, what do you think?

I'm considering the SUMO.

#56 (.177 / .22) looks like what I need, but I'm scared of baffle strikes happening.

So, you reckon I ought to go with #561 (.22 / ..25)? (it's the third one down)

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The .177/.22 is already one size up from your .177. I have a Tanto in my .177/.22 Streamline & it works just fine. Chances are that if you have baffle strikes it will be from a rifle with unaligned threads. The chances of having a misaligned Donny are extremely, extremely low. I have 4 Donny's on various rifles and Zero problems with any of them. Get whichever model you believe will look the best on your airgun. Also make sure you get the correct threads. Donny will know what you need.
 
Thanks for all the help, guys. I was considering the SUMO because that's what I have on my Daystate Wolverine .25 R, HP and it does a great job quieting it down.

I think the TANTO, at 1.22 x 5 inches, will be good on the .177 Avenger. The separate Avenger adapter that feeds into the shroud is supposed to move the mod farther out so one can remove the Foster fitting cover without having to remove the mod every time you want to re-fill the gun. I think the skinnier TANTO would do perfectly.

I'm about to call DonnyFL and place my order for a TANTO.