For removing the backs of watches that screw on (screw-back).

These are small and portable, ideal for antiques dealers and anyone who travels around. You could, however, struggle getting enough leverage to open 'stuck' watch backs.

STANDARD

2.5 inches X 1 inch.
Minimum watch back size 15mm.
Maximum watch back size 55mm.
The prongs are 'hooked' as shown in top picture. 

JUMBO

3.25 inches X 1.5 inches.
Minimum watch back size 23mm.
Maximum 70mm (that's large!).
The prongs are 'round' as shown in the picture.