A baraita with the 4 different methods by which a buyer can acquire merchandise -- for example, dry good. That is, until the measuring cup (as it were) is filled, as per their terms, at which point, the seller cannot renege. If the buyer owns that vessel, however, then the buyer takes full possession from the time that the good reach the vessel. Plus, what happens if the goods are deposited with a guardian or custodian? When does the transfer of ownership occur? Also, the search for a parallel question of acquisition conundrums, which leads to Gittin - bills of divorce. But the Gemara concludes that the bills of divorce are not actually a good parallel case.