Chris and bpounds are both right. Adding to that, my experience is they are on 24" centers when aluminum studs....16" C to C if wood studs. And I think most exterior wood studs are 2X3. While interior studs are 2X2. Not sure of the size of alum. studs.
'12 F350 SB, CC, SRW, 6.7 PSD, 3.55 RAR, 6 spd auto
2015 DRV 38RSS 'Traditions'
Pullrite Super Glide 18K
Retirement = It's all poops and giggles....UNTIL someone Giggles and Poops.