The 4" Gorilla Tube is the second generation bait responsible for my personal best (13.24lb. LMB - Photo on our home page). The mold is just like our other tube molds, it makes an awesome bait. The spline fits like a glove and there is no flashing.
The body is 2" to accommodate a 3.0 EWG. If you trim the 2.25" tail flush with the flaps the overall bait will be approximately 3.25". So the bait can be as long as 4.25", or as small as 3.25" (and still have a 1" skirt).
This is a great bed bait, flipping bait, jig trailer, Carolina rig, T-Rig, etc. If you haven't fished a tube before this is a great one to start with as it has lots of movement and is very productive using it the same way you would a creature bait.
Here's a fishing tip that works great on most tube baits (T-Rig or C-Rig): plug the opening of the tube with a small piece of worm and hold it in place with a toothpick. This will trap the air in the tube and cause it to float off the bottom. Make sure you don't lay your rod down - you very well could loose it!!!
If you have one of our molds that already has a skirt (uses a spline - the part that makes the tail) you do not need to buy another one if you don't mind swapping out the tips. The spline can be used in any of the regular skirted molds. If you don't already have a spline (one of our skirted molds), you will need the spline to make the tail. You can order the spline and insert by clicking on the appropriate item in the table above. 
