What bulb does the E34 turn signal use? I'm confused between PY21W, 1156, and 7506...which one is it?!?!?

I finally put in my clear corners and the stock bulbs are clear, I would like to put in those silverstar bulbs but i'm not sure if 1156 is the same size as py21w or 7506. PO has a spare in the trunk that are 7506 but I dont see any 7506 bulbs @ advance that are amber only 1156 or 1157. 1157 are dual filaments and i'm pretty sure E34 use single filaments but yeah any help is appreciated!