You should be able to distinguish the difference, these are both LS, the non splined side is 3.5” and the splined side is 4”.
They are turned opposite to each other, and you can notice the difference in the bottom crinkles to each other, hope this makes sense, I can post a pic with a ruler, but as Tom Cat says and I’ll confirm 4” splined side and 3 1/2” cover side.
By the way the dust cap is also smaller diameter too, and I need 2 of them.
They are essentially the same hub, just that your supplied one is for a later model, and will work front and rear, and will be easier to find the dust covers.
Cheers