How slim is jim?

I'd say this toy is on the slender side without being too small. If you have a specific size in mind, remember that each toy on this site has measurements readily available, and most have a real-size example button below their pictures. The measurements from the product info page are as such:

Length:
6"
Insertable length:
5 1/2"
Circumference:
4"
Diameter:
1 1/4"