A retention housing for the outer race of a ball bearing for a high pressure spool of a gas turbine engine, the retention housing comprising: a ball bearing housing defining a cylindrical inner surface that is disposed equidistantly from an axis of rotation that extends in an axial direction, a radial direction being defined in a direction that is normal to the axial direction, the ball bearing housing defining a forward end disposed axially spaced apart from an aft end; a spring finger housing disposed radially apart from and radially outwardly from the ball bearing housing and disposed concentrically around the ball bearing housing, the spring finger housing defining a forward end disposed axially spaced apart from an aft end, the forward end of the spring finger housing being connected to the forward end of the ball bearing housing; the spring finger housing defining a plurality of axially extending fingers, each finger defining a forward end and an aft end disposed axially spaced apart from and opposite to the forward end of each respective finger, each finger being spaced circumferentially apart from each nearest adjacent finger, the plurality of forward ends of the fingers forming a monolithic structure with the spring finger housing, and the plurality of aft ends of the fingers forming a monolithic structure with the spring finger housing; the retention housing being characterised in that the aft end of the ball bearing housing defining a plurality of blind bores, each blind bore extending in the radial direction and defining an open end; a plurality of dowel pins, a respective one of the plurality of dowel pins being disposed in a respective one of the plurality of blind bores; wherein an end of each respective dowel pin that projects out of a through bore defined radially through an interface shell defines a free end that is spaced apart in the radial direction from a blind end of the respective blind bore and defines a radial gap between the respective free end of the respective dowel pin and the respective blind end of the respective blind bore. a ball bearing housing defining a cylindrical inner surface that is disposed equidistantly from an axis of rotation that extends in an axial direction, a radial direction being defined in a direction that is normal to the axial direction, the ball bearing housing defining a forward end disposed axially spaced apart from an aft end; a spring finger housing disposed radially apart from and radially outwardly from the ball bearing housing and disposed concentrically around the ball bearing housing, the spring finger housing defining a forward end disposed axially spaced apart from an aft end, the forward end of the spring finger housing being connected to the forward end of the ball bearing housing; the spring finger housing defining a plurality of axially extending fingers, each finger defining a forward end and an aft end disposed axially spaced apart from and opposite to the forward end of each respective finger, each finger being spaced circumferentially apart from each nearest adjacent finger, the plurality of forward ends of the fingers forming a monolithic structure with the spring finger housing, and the plurality of aft ends of the fingers forming a monolithic structure with the spring finger housing; the retention housing being characterised in that the aft end of the ball bearing housing defining a plurality of blind bores, each blind bore extending in the radial direction and defining an open end; a plurality of dowel pins, a respective one of the plurality of dowel pins being disposed in a respective one of the plurality of blind bores; wherein an end of each respective dowel pin that projects out of a through bore defined radially through an interface shell defines a free end that is spaced apart in the radial direction from a blind end of the respective blind bore and defines a radial gap between the respective free end of the respective dowel pin and the respective blind end of the respective blind bore.