Collars

Cobra Design - measure your dog's neck snugly in inches, then add 0.5inch for this pattern to fit 2 fingers under the collar.
Shark Jawbone Design - measure your dog's neck snugly in inches, then add 1 inch for this pattern to fit 2 fingers under the collar.
Zig-Zag Design - measure your dog's neck snugly in inches, then add 0.5inch for this pattern to fit 2 fingers under the collar.

Bracelets

Measure wrist circumference and take that measurement as the tightest fit. The 2-inch adjustable scale gives you the option for a more comfortable/loser fit. For example; the wrist measures a snug 6 inches choose small, the wrist measures a snug 5inch choose extra small.

Extra small: 4-6 inches
Small: 6-8 inches
Medium: 8-10 inches