This is a ventilation frame designed to prevent stuffiness caused by a backpack sticking to your back. By creating a gap, ventilation is improved, and it makes a huge difference. It's very lightweight, around 100g. I bought it for travel, but the zip ties made it cumbersome to switch between different small backpacks, so I stopped using it. It's perfect for those who use the same backpack all the time. Please check the official website for how it looks when in use: https://vauclusegear.com/products/ultralight-ventilation-backpack-frame?srsltid=AfmBOorGPKx0YzLzuO0YTDFk9qa53bHP4XcwhVpb2QwJWqX3PfpctEY4 Also, there's a video with a more detailed explanation by a shop in Japan, which you might find helpful: https://www.youtube.com/watch?v=t7dD_4hFlgg