Sometime in the later 15th century the idea of the gussett came about. Breast plates can only be a finite distance across the chest so as not to interfere with arm movement. Gussetts are plates installed at the arm openings that float on slot rivets allowing the breast plate to be wider, thus covering more area without hindering arm movement as the plates collaps inside the breast plate with arm motion. While gussetts are avaliable as an option on our breast and back plate sets there are a fair number of folks who already own one of our sets who we thought might want this feature so were offering it as a separate item. Just get your MT breast plate to us and we'll install them and get it back to you. Please specify 1", or 2" wide gussetts when ordering. Suitable for later 15th through 17th century use. HAND MADE IN THE USA.