It just came to my attention that there's a "big" difference between different brands.

My Hammer Vibes and Anger, Brunswick Alpha Max, and 900 Global Look all have about 3/8 in. thick coverstock; while my R/G Original Cell and Storm Victory Road have "much" thicker, about 9/16 inch thick coverstock.

While none of them has cracked, wouldn't balls with thinner coverstock get saturated with oil faster and lose reaction sooner? Also wouldn't those ball cost less to make and should be less expensive?

Thickness will very by ball and by where you check in some cases. Many of the bigger cores that have come along over the years have lead to much thinner coverstocks in certain areas of the bowling ball.

A few manufactures like, Visionary, had no fillers if I am not mistaken. Just core then coverstock.

It's a little cheaper to make a ball with no outer core due to less labor being involve, but you don't have as much flexibility in RG and diff.  That is why most 2 piece balls are higher RG lower diff balls.

As for transferring more energy to the pins, there are limits on the coefficient of restitution, so……...

A ball with no "filler" material, just cover and core, would probably weigh 20 lbs...

There has to be something between the core and cover and I would LOVE to see actual proof of any such claim that "we use no filler" in our balls.  Find one for me to cut in half...  Ask your self this question:  If a dense core were surrounded by dense coverstock only, what significance would the core even have? 

On topic, I have not noticed any measurable difference in performance, oil absorption, or cracking with shell variations.  Each ball has a minimum and maximum circumference when it leaves the factory.  Some get more cover removed than others due to machine variations and possibly human error.  Not a big deal either way to me.

I had a conversation not long ago with a former Ebonite staffer about this subject.  He told me something I have not heard, but make sense.  He said the cover thickness isn't so much about cracking, but that the thinner the cover, the quicker the shell gets saturated with oil.  He said that Ebonite always had thinner shells than some of the others, and it is true that they have about the worst reputation for dying quickly. 

Also a guy who drills for me said that Brunswick shells got thinner when they first moved to Mexico, but that many of them got thicker again a couple of years ago.  I know the old PK 18 and activator shells were among the most durable out there.  Not sure about the newer stuff in the last 5 or 6 years.

It is definitely possible to make a true two piece ball with no filler.  If I had a band saw I'd cut a ball in half for you.

I'm not saying it's not possible, but what would it weigh?  What significance would these "dynamic" weight blocks have on it?  It would be like rolling a ball bearing down the lane...

The core is still more dense than coverstock material, you just can't get the RG's low or the diff high without filler material.

Thanks Jeff,

I'm still waiting to drill into one of these "magic balls".  Can we agree that IF the core is surrounded by a "more dense" coverstock material the weight block will have less effect?  See post by "itsallaboutme".

Think of the clear polyester balls.  As far as I can remember they started at 14 lbs. and they go STRAIGHT!  Extreme dry lanes will make anything move a little...

Some companies may use DIFFERENT material between their core and cover, and choose not to call it filler, but...