  In the upcoming IceCube-Gen2 extension, the newly developed optical modules
will include 4-inch PMTs. For this purpose, the manufacturers Hamamatsu and
North Night Vision Technology have developed new PMT models to meet the
requirements of the IceCube-Gen2 science case. The specifications include
strict requirements on temporal resolution, detection efficiency, and dark
noise. We summarize the efforts to measure these performance characteristics
and show that both PMT models meet the performance specifications set by
IceCube-Gen2. Prototype optical modules based on both PMT models will be
deployed with the IceCube Upgrade in order to test them in situ and help decide
on a vendor for the Gen2 extension.
