Easton's 5MM Match Grade HIT Collars, made of hardened stainless steel, are designed to enhance the impact strength of arrows using the HIT system. They are included with Easton's 5MM Match Grade arrows, but can also be purchased separately to fit many 5MM arrows on the market. These collars are compatible with 5/16 field points.
It fills in any space between the collar and the shaft due to tolerance differences.