These mix-and-match instances in the beta program were interesting, but not exactly compatible with most enterprises. Google allowed customers to create virtual machines with 1 CPU to 32 CPUs and memory up to 6.5 GiB of memory per virtual CPU. The catch was that these custom instances were for CentOS, CoreOS, Debian, OpenSUSE and Ubuntu.
Now Google has Custom Machine Types for Red Hat and Windows operating systems. The Red Hat and Windows offerings cover most enterprise data centers.
Custom Machine Types have flat pricing based on memory and virtual CPU.
It remains to be seen how popular custom instances become in the enterprise, but it's clear Google is looking to differentiate itself from Amazon Web Services.