How many different buffer tube lengths?

[Dolt]

I have a spare ar 15 stock and I can't ID the proper length buffer tube for it. The stock is shorter than an A2 stock but longer than a collapsible stock. Anybody have any ideas how to determine what length tube fit it?

I used to know this stuff, but as I get older I get stupider and stupider.

[gwp]

The standard A1 stock is shorter than the standard A2 stock. The standard A1 and A2 fixed stock use the same length buffer tube (receiver extension) but a buttstock spacer and longer screw is used for the A2 stock.

http://www.brownells.com/rifle-parts/stock-parts/butt-plate-parts/buttstock-spacers/a2-buttstock-spacer-prod24055.aspx