Gripper Options
With the exception of the Smooth inner / Smooth outer (25A / 12A)
Grippers are Shore A25 for inner gripper and A18 for outer.
wikipedia article on Shore durometers for further explaination.
https://en.wikipedia.org/wiki/Shore_durometer
Using the graphic, determine your choice. The most comfortable is smooth inner / smooth outer. That comfort comes at the price of less gripper holding at higher pressures.
Smooth inner / Smooth outer (25A / 12A) is a popular choice for balloon use.