Welcome to the forum.
That is a carbine tube as has been said. The only way to get shorter is a pistol tube. However, you would need a shorter buffer of the same weight with an appropriate spring to get the same recoil. A possible option to get closer to the optic is the MFT Minimalist stock. They are available if you search.
Post a picture of your rifle so we can see it. What optic do you have? What is the eye relief supposed to be?