Black bushes for wiper wheelboxes. Sold as a wiper wheel box set(one above the windscreen scuttle cowl and one under the cowl), takes two sets per car.
To fit early Mk1/2 cars cut down the part that fits under the panel work part(this part has a ridge) by about 4mm or use old bush as template.
Actual overall lengths are 22MM long for part with ridge and 22.4MM for outer part on the MK1 mini.