The ornamental design for a ringbasin, as shown and described.
FIG. 1 is a top and side perspective view of a ring basin showing a new design;
FIG. 2 is a front side view thereof;
FIG. 3 is a back side view thereof;
FIG. 4 is a left view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top side view thereof;
FIG. 7 is a bottom side view thereof;
FIG. 8 is a sectional perspective view thereof taken from line 8-8 in FIG. 5;
FIG. 9 is an enlarged perspective view thereof taken from area 9 circumscribed in FIG. 8; and,
FIG. 10 is an enlarged sectional perspective view thereof taken from area 10 circumscribed in FIG. 8.
The measurement values shown in dashed lines on FIGS. 1, 6 and 8 show environmental conditions only and form no part of the claimed design. The dot-dash-dot broken lines in FIG. 8 of the drawings depict the boundaries of the enlarged views that from no part of the claimed design. The dash lines shown in FIG. 7 depict portions of the ring basin that from no part of the claimed design.