The invention relates to a radial compressor (1) for an exhaust gas turbocharger, in particular of an internal combustion engine, with a compressor housing (2) comprising an axial inlet channel (3) and a radial outlet channel (4), with a compressor wheel (6) for delivering and compressing a gas, wherein the compressor wheel (6) has an axial inlet side (7) facing the inlet channel (3), a radial outlet side (8) facing the outlet channel (4) and an axial wheel surface contour (9), which extends from the inlet side (6) as far as to the outlet side (7), with an adapter element (10) which is substantially designed sleeve-like, which can be axially introduced into a fastening section (11) provided on the compressor housing (2), wherein the adapter element (10) at least in sections has a surface contour (13), which is designed substantially complementarily to the axial wheel surface contour (9), so that by axially moving the adapter element (10) in the fastening section (11) a gap width (w) of a passage gap (14) axially formed between the adapter element (10) and the compressor wheel (6) along the surface contours (9, 13) facing one another can be adjusted.