Tiny Turbo Changers have codes. Ignore the embossed four-digit number - right next to the tiny window in back of the bag will be one embossed letter. This is your blind bag code.
The codes are:
A – Grimlock gold
B – Grimlock black
C – Lockdown
D – Hound
E – Bumblebee yellow
F – Crosshairs
G – Blackout
H – Soundwave
J – Starscream
K – Sideswipe
L – Bumblebee black
! – Prime
Also, Grimlock is small and thin.