CHICAGO (CBS) — Chicago’s window washers are on strike for increased wages and benefits. They have been on strike for nine days.

Early Tuesday, workers gathered at Millennium Park wearing some interesting attire – superhero costumes.

The costumes were similar to what they wear when scaling Lurie Children’s Hospital.

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The window washers are asking their employer, Corporate Cleaning Service, to come to the bargaining table in good faith.

Corporate Cleaning Services responded saying they operate on a commission-based system and that the minimum amount paid to a high-rise window washer for seasonal work is nearly double what the union claims.