A connection device may include an insertion section having an annular outer groove. A housing may be configured to receive the insertion section and a blocking element may be configured to lock the insertion section in the housing. The blocking element may have a band-shaped core and a plurality of teeth arranged adjacent in the peripheral direction along the core. Each of the teeth may include an outer tooth section and an inner tooth section. A core profile may have a core principal direction determined by a maximum diameter. The teeth may have a tooth profile which has a tooth principal direction determined by an inner flank of the teeth lying radially on an interior of the outer tooth section and the core principal direction may be inclined with respect to the tooth principal direction.