This is my FIRST Soft plastic worm mold. Frankly, I don't even own an injector but the opening is 5/8 in diameter and about .500" (1/2") deep from the outer surface. Google said that 5/8 is the standard size for injector. From the 5/8 opening, there's a .200" diameter hole into the cavity. I've also added four 1/4" (.250) holes so you can either bolt it together or use some type of dowel to keep it from shifting.

3.5" soft plastic worm. It's suppose to wobble as it fall. Can rig it as wacky worm, or Carolina rig.

To see the action: https://youtube.com/shorts/ubVVzZNIYB8?feature=share