The card artwork depicts a Double Lead Bloon punching a blue punching bag with a drawing of a happy Monkey's face taped onto it. The chain for the punching bag snapped. In the background is an empty boxing ring and the interior of a gym.
Compared to most Double Bloons, Double Leads are less susceptible to low-hit damage, which Barrel of Monkeys struggle. However, they're a little slower than Double Yellows for the same cost and much rarer, but do more potential damage.
Unlike Double Yellows, Double Leads can take two Long Range Rangs without getting destroyed, leaving 10 Health outside of Dark Castle or other Health modifiers.
Try to use high-damage attacks on Double Leads first. Storm Of Arrows does significant damage, and Super Monkey Storm can one-shot them.
Double Leads are not often used by human players. For the same cost, they're slower than Double Yellow Bloons, but for 2 extra Gold the Double Ceramic Bloon poses more of a direct threat. The added Armor is less impactful because many human players equip high-damage and/or Armor Piercing Monkeys.