Intention: Get your speed up in the 50 or 25 Build, starting slowly and gradually speeding up, which will help you to swim fast with good technique. In the 100 or 50 Freestyle @ 80% really try to swim strong with good technique. You can test this by counting your strokes and make sure your number is not up that much higher.
Warm up: 400 Choice
4 x 50 (25 Scull Build / 25 Freestyle Easy) - 10sec rest