This is a 25mm hose clip. It has various uses for many vehicles some of which are listed below

T1 Beetle - Pipe clip for fuel lines / Headlight washer system
T2 Baywindow Fuel line clips / Headlight washer system
T25 Clip for cylinder head ventilation on Diesel models / Hose clip on the intake system on Waterboxer / Used in the power steering system
Golf / Jetta / Corrado. Use for the fuel gauge sender / Pipe clip for throttle valve on 1.8 PG Engines
T4 Transporter Used in the headlight washer system / Used in the vacuum system on 2.0 Engines 4 Cylinder
Used in the cooling system of early Golf engines