hard disk unit for DEC drive for PDP-10 & PDP-11 oem systems takes a 12 inch hard disk.
That RK05 honey can take a big one! System diag on LVDT humps the whole rack & after 50 tracks starts long strokes...
Tokyo babes love big DEC mainframe's pdp-10 had to push big 12 inch hard disks into RK05.
( LVDT = linear variable displacement transformer ) LVDT moves the head in & out ..