1/4 is a touch less than 3/8" thick and 3/8 is just shy of 1/2" thick.
Thank you to you both!There are the heights of the head and the head including the selector lever. The Matco, GW, and Tekton are the thinnest "standard" ratchets I've seen. Edit- standard meaning not 3/8 in a 1/4 body which will have reduced torque capacity based on lower gear height.
1/4: .36 / .41
3/8: .48 / .54