Hitch Lock: Universal trailer coupler lock to secure caravan, trailers; fits 48 mm, 51 mm and most 59 mm trailer couplers Maximum Security: Aluminium body; locking mechanism resists picking and prying Outdoor Use: Raw material resists to rust and corrosion; for outside use Specifications: (H x W x D) 6 x 13.5 x 9 cm; two keys included