AR Pistol - Size Restriction On Upper?

[insin]

Hello all,
I was just wondering if there is a size restriction on the choice of upper is one is going to get a pistol AR? I see alot of 7" uppers on pistols, but hypothetically, could one use a 10", 12", or 14.5" upper on a pistol lower here in California?

I don't think there should be a problem if the upper is any size as long as it was less then 16", or am I wrong here?

Thank you

[CSACANNONEER]

Any size you want to.

[FNH5-7]

Any size you want to.

^^This^^

Any size otherwise considered SBR if it were accompanied by a stock. Kinda pointless to have a 16 or 20 inch upper in pistol configuration.

[insin]

Any size otherwise considered SBR if it were accompanied by a stock. Kinda pointless to have a 16 or 20 inch upper in pistol configuration.

Yeah, 16 or 20 is kinda unreasonable, however i just wanted to make sure I wasn't missing something in which route someone could go when configuring their AR pistol. Thanks for the replies.