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.

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.