This 1.25" cap allows you to protect your 1.25" eyepieces. It fits on the barrel end (base) of the eyepiece that you insert into the focuser. It is made of hard black plastic and has a flat base so you can stand the eyepiece on end. This caps does not generally fit the top ('eye end') of 1.25" eyepieces - for that please see the other caps in this store.