Fillister (Phillips) Head Self-Tapping Screw for interior trim. 20mm length with a wide and low profile head. Designed for screwing into plastic.  Sold in packages of 8 screws.

Overall length is 20mm or about 3/4 inch with a diamter of about 1/8 inch or 4mm.

Used to attach interior trim pieces in the following models:

2002-2006 R50 Cooper and Cooper S Hatchback
2005-2008 R52 Cooper and Cooper S Convertible