Now UI Kit - A beautiful Bootstrap 4 UI kit. Yours free.
Bots UI Kit - Fully customizable Sketch UI Kit for Messenger Platform
Dashboard UI Kit - A modern & responsive dashboard UI kit for designers.
Landing UI Kit - Handcrafted UI components for landing pages
Bootstrap Zero - Open-source, free Bootstrap templates collection.
Cards - Webflow UI Kit - Free Clonable UI Kit prepared fully in Webflow Designer