These are the spacers designed for the folks that want to run newer style 04+ rear top hats on older style 02-03 struts. Perfect example of this is if you want to run say a set of 04+ springs on Tokico D-specs. Normally there would be a gap between the top hat in back which would lead to clunking. You could stack washers to fill it, but that involves some trial and error. With the 921 spacers you just slip these on and your ready to go.

(These are for the rear two top hats, the fronts don't require these).