The 3/8" DIY version was made to be the "every man's tool" Affordable enough for every guy to have in their toolbox.
Outfitted with the same low friction UHMW low friction bushings and chrome vanadium gears, the DIY version has some of the same high-quality parts the professional models use.
The DIY is a great tool for around the house and the garage giving you an 8" extension for your "tite" places.
The biggest difference between the DIY wrench and the Pro models is the housing is made from ultrasonically welded plastic.