Garrett GBC any model including GARRETT GBC17 - GBC20 - GBC22 as GT28 with hole for closed type turbine exhaust impeller for external wastegate, with hole for 50mm turbine exhaust impeller that can be expanded as desired and in any case excellent if you want to support a pipe and weld it comfortably, in any case the diameter of the GBC 350 is more than sufficient as the exhaust impeller that you see measures only 46mm.
Flange useful when using a separate external wastegate so you can close it by making a hole and threading the door with a bolt or by welding the turbine wastegate door directly.