When installed on the front wheel, there’s no need to carry a second lock to ensure maximum security.
From the Manufacturer
Gravity locking system that secures to your front wheel. Easy installation, only requires a 15mm wrench (No keys). Wheelnutz provide internal "lock-out" function and can only be removed by turning the bike upside down 180 degrees. Use in tandem with Messenger Mini to create a complete locking solution for your bike. Weather protective coating keeps Wheelnutz from corroding. In addition to popular M9 thread, M10 (001775) and 3/8-Inch (001782) also available
Kryptonite Wheelnutz M9 Bicycle Lock - B00NGDS2Q2