This is a replacement part for the Echo Sport Trigger. You do not need to purchase this item unless the part that came with your Echo Trigger has been lost or damaged. This relates to part U on the parts diagram that came with your trigger. If you no longer have the original parts diagram that was included in your Echo Sport booklet, you can find a pdf copy of the booklet on our website. Please navigate to the home page and scroll all the way to the bottom of your screen. There is a section in the footer titled manuals with pdf copies for each Echo Trigger.