A rock drilling shank adaptor comprising: an elongate body having a first end to be positioned towards a piston and a second end to be positioned towards a drill string; the body comprising an axially extending internal bore to allow passage of a flushing fluid to the drill string via the second end; a flush hole extending radially through the body to the internal bore, the hole having an axially forward region positioned closer to the second end than an axially rearward region positioned closer to the first end and having a radially external side positioned at an external surface of the adaptor and a radially internal side positioned at the internal bore, the external and internal sides coupled via a generally radially extending surface that defines the flush hole extending through the body; characterised in that: the flush hole at the axially rearward region is reinforced relative to the axially forward region in that in the radial direction from the external side to the internal side, a surface at the rearward region at least at a radially inner portion is curved or aligned transverse relative to a radially innermost portion of a surface of the hole at the axially forward region in the radial direction such that the surface of the rearward region at the internal side is positioned axially closer to the second end than the surface of the rearward region at the external side. an elongate body having a first end to be positioned towards a piston and a second end to be positioned towards a drill string; the body comprising an axially extending internal bore to allow passage of a flushing fluid to the drill string via the second end; a flush hole extending radially through the body to the internal bore, the hole having an axially forward region positioned closer to the second end than an axially rearward region positioned closer to the first end and having a radially external side positioned at an external surface of the adaptor and a radially internal side positioned at the internal bore, the external and internal sides coupled via a generally radially extending surface that defines the flush hole extending through the body; characterised in that: the flush hole at the axially rearward region is reinforced relative to the axially forward region in that in the radial direction from the external side to the internal side, a surface at the rearward region at least at a radially inner portion is curved or aligned transverse relative to a radially innermost portion of a surface of the hole at the axially forward region in the radial direction such that the surface of the rearward region at the internal side is positioned axially closer to the second end than the surface of the rearward region at the external side. the flush hole at the axially rearward region is reinforced relative to the axially forward region in that in the radial direction from the external side to the internal side, a surface at the rearward region at least at a radially inner portion is curved or aligned transverse relative to a radially innermost portion of a surface of the hole at the axially forward region in the radial direction such that the surface of the rearward region at the internal side is positioned axially closer to the second end than the surface of the rearward region at the external side.