I bought the OTC and it is a really nice unit. It looks like it is the same exact unit as the Mac Tools one made in the same place (China) just packaged with different branding. I looked high and low for an American Made Leakdown tester but only came across 3 different styles of the higher-end testers and their designs and manufacture were shared across several different Brand Names. DO NOT buy the Harbor Freight one. Instead of giving two accurate gauges for reading to differentiate the PSI loss the HF has a PSI and then a percentage gauge. It also runs at only 15PSI when the OTC can do 100PSI.