Bands act here as a form of accommodating resistance. As you bring the weight up, the resistance increases. And as you lower the dumbbells, you have to fight against the regular weight, but also the band resistance trying to pull you down.
Wrap a band around your back.
Lie down on a flat bench holding dumbbells or kettlebells at your shoulders, palms facing inwards. Bring the dumbbells up until your arms are almost fully extended.
Slightly bend your arms and arc the weights down to your sides until you feel a stretch across your chest.
Squeeze your pecs to return the weights to the start position.