Carb barrel gaskets are most often called intake or manifold gaskets.
Get your caipers out & measure the inlet opening then measure the outlet.“Yes, that!” -Lord Helmet, Commander of Spaceball 1
carbnclean - if you don’t know, the barrel of the carb is the primary air passage through the carb - more commonly known as the venturi. Technically speaking, however, a venturi should have a reduction in diameter and, in my experience anyway, is not a typical feature on these small engine carbs.
Almost every 4 cylinder small engine carb I’ve worked on the last 50 years has a Venturi. Some may not be a necked down as you would think, but it is there. Most of those that look straight are slightly smaller and with the extended main nozzle helping, they are smaller in area producing the Bernoulli effect or principle To draw in fuel.
Get your caipers out & measure the inlet opening then measure the outlet.
Guess which one is smaller ?
Usual method of working out which gasket goes where.
The one with the smaller hole goes on the engine side