Classify the following boxers as either Heavyweights, Welterweights, or Lightweights. 

1. Gervonta Davis
2. Terence Crawford
3. Errol Spence
4. Tyson Fury
5. Devin Haney
6. Andy Ruiz
1. Lightweight
2. Welterweight
3. Welterweight
4. Heavyweight
5. Lightweight
6. Heavyweight