For decades I've use 4"  tubes that are on the soft side. 

Using soft rubes with a tube bait jig head is a problem as it tears up the front of the tube on the strike therefore requiring re-rigging.

I'm interested 3.5" tubes, that are readily available in stores, that are on the harder side. Not interested in slim 3.5" tubes,

Thanks.

Bob

I use a weighted tube hook that requires re-tying when you need to replace the tube, and soft tubes fish well but can be frustrating sometimes (especially when you bi-catch pike or pickerel frequently).  Switching to Z-Man's tubes is an easy solution if you wanted 4" tubes...

Tight lines,

Bob

I see what you're getting at. Big bite baits 3.5 tube is made of solid tire rubber it seems, so much so I usually take one and work it in by hand before I will throw it. Very durable. There's another brand I've used in the past that makes a harder comp tube, mizmo, that seem to be on the tougher side too.