These thick resistance bands are great for that extra level of tension. Can be used by themselves or with strapping them to gym equipment.
Each colour represents a different width and therefore resistance:
Orange - 0.64cm (max 10kg)
Red - 1.3cm (max 20kg)
Blue - 1.9cm (max 26kg)
Black - 2.1cm (max 30kg)
Purple - 3.2cm (max 45kg)
Green - 4.5cm (max 75kg)