It's a 1/2", but SumOne is right ,which I just found out myself! How infuriating of Hipshot...
So if it's anything like the Skyline, I need to buy an adapter
https://hipshot.zendesk.com/hc/en-us/articles/360021168871-Which-Xtender-fits-a-Lakland-Skyline-Bass-
"Most Lakland Skyline Basses use our Licensed 1/2" Ultralite tuning machine, which fits a 5/8" (16mm) peghead hole. Our 1/2" Ultralite Xtender is designed to fit an 11/16" (17.5mm) headstock hole. However, we offer a special 5/8" adapter nut that allows it to work seamlessly with the Skyline."
https://hipshotproducts.com/products/adapter-nuts-and-bushings?variant=12797827285091
Postage from Hipshot is $65, for a $4 part. Does anyone know of any substitute I could use?