Its just long enough that it touches the headliner and the puts a hint of tension between the metal roof and the headliner material.
Im in the air force and its pretty common near Remembance day to keep spares in your car as they sometimes fall apart or the seatbelt eats them when in uniform when you get in or out. So it was handy.
I imagine just about any sewing needle would work.
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View my fuel log 2015 Micra S automatic: 7.9 L/100 km ... 35.7 mpg (Imp) ... 12.6 km/L ... 29.7 mpg (US) ...