These are leather (or synthetic) finger loops for flow floggers (purchased separately in the store). These can include a quick-change clip at your discretion for versatility, otherwise they will be integrated into the flow flogger's chain.
 
These are commonly a stiff black leather or vegan leather for best performance. (4-5 oz)
 
More colorful leathers are an option, but they will stretch over time (3-4oz)