Something to mix your chest workout up. Aim for 100 reps with a weight you feel comfortable with (or uncomfortable to be honest), but do it in as many sets as you need. Could be 10 sets of 10, could be 20 sets of 5. Just get the 100 reps done. Would advise doing it at the start of your chest workout. Will really shock the muscle. I shot for the 40kg dumbbells. This was the last nine to make it 100. This was on an incline but can obviously do the same on decline/flat bench.