Fostech Echo Sport Trigger Install. A small portion of the selector paddle sticks out from under the trigger guard and it is etched echo on the left side and semi on the right side. Make sure the spring stays in the notch of the trigger pack:

It is also a ton of fun. My sports trigger exploded when the package was opened and the directions to reassemble are terrible. Once the trigger lock is in the correct position, pinch the parts from the sides to hold everything in place.