1. 【High quality materials】 The bicycle trailer hitch attachment made of steel with black enamel coating, made of durable iron material, strong and durable, corrosion-resistant, difficult to damage.^ 2. 【Appropriate size】 The diameter of the ， rear axle mounting hole of the bicycle: 11mm ， Diameter of the mounting hole of the connecting trailer: 7mm ， The diameter of the recessed portion where the shaft nut is screwed: 21mm ， Base plate length: 55mm^ 3. 【Ensure safety】 Every bicycle trailer is equipped with a connecting pin. The pens can hardly be opened. Even once you have them installed, they do not fall off easily and can keep your baby safe.^ 4. 【Easy to Install】 First, attach the tow bar of your bike trailer to your bike with a screw nut. Then insert the trailer attachment; Finally put on the pen; The connection is ready, bring you a lot of convenience.^ 5. 【Wide application】 You can use it to pull strollers and pet strollers, and bring children and pets when you ride a bike in the park, which is very convenient and safe.^