Lifting Sub is designed so that you can lift on the face (lip) just above the box, or so that you can bite on the sub body itself for lifting purposes. They are used with YC elevators, side door elevators and slip type elevators. The maximum weight that can be lifted with a lifting sub (design 1 to 3) is the lesser of either the tool tensile strength or the connection tensile strength. These values are a factor of material strength.
Lifting plug long and short (tool length) are designed for side door elevators where contact with the pipe is permitted.