Which Bass Extender for US SUB?

[gluvhand]

Hi all. I'm looking to maybe buy a Hipshot Bass Extender for my US SUB. I'm pretty sure I need a BT1 but do I need the short or standard key? Any help would be appreciated.

 

[rhythmCity944]

You need a short key post BT1 style.

 

[gluvhand]

You need a short key post BT1 style.

Thanks. Appreciate it.