Mountainsmith have been making dog packs for 40+ years and have perfected their design, offering a 4-point adjustable chest harness with sternum pad, independently adjustable back harness, adjustable belly strap and a metal D-ring to attach the lead.  It is equipped with 2 pannier compartments with zippered accessory pockets, mesh panels against the dogs body for ventilation, reflective trim for safety and has a weather and water resistent coating. It's available in a medium size suiting dogs between 40-90lbs or approx 18-40kg, roughly labrador size. Chest girth between 24-40 inches or 61-101cm. Available on amazon for over £85