I have a Lowepro Commercial AW camera bag. As the name suggests, this is a big bag, capable of holding multiple full-size DSLRs and several lenses. The main interior compartment is about 18.5" x 9". I used it to carry my kit to shoots, but now I have a rolling bag and a mirrorless camera and no large lenses that warrant this size bag. I think it could easily hold a Tamron/Sigma 150-600mm lens and perhaps even a Sony or Nikon 180/200-600mm with some room for the camera. Thank you for your interest.