Ford F-150 Owner's Manual page 46

Seatbelts
If, because of body size or driving position,
it is not possible to properly fasten the
seatbelt over your lap and shoulder, an
extension that is compatible with the
seatbelts is available free of charge from
Ford Motor Company dealers. Only Ford
seatbelt extensions made by the original
equipment seatbelts manufacturer should
be used with Ford seatbelts. Ask your
authorized dealer if your extension is
compatible with your Ford vehicle restraint
system.
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F-150 (TFC) Canada/United States of America, enUSA, Edition date: 201607, Second Printing