1.0.0-rc.7 is a release file of the Minecraft mod Cotton for Fabric, made for Minecraft 1.15-Snapshot, 1.15, 1.15.1. It was published on December 30, 2019 and is 0.5 MB in size. For the full description, screenshots and every other version, visit the Cotton mod page.
How to install: Put the .jar into the mods folder (.minecraft/mods) and start Minecraft with the matching mod loader profile.