The ones for the turning lights (if that's the correct nomenclature) are single filament/single contact (on the bottom).
The dual filament/dual contact are for like tail lamp/brake light on the same bulb.
I just had the Vette out tonight & it makes a nice difference.
Did my first burnout tonight, last one out of the gym & empty lot. 3000 rpm & fast clutch out, pretty cool, I eased off the throttle after 20 or 30 feet, coulda gone more. Tires $$$.
I picked up some Silverstars tonight too, next project - Sunday.