Bought this to take my cats to the vet while I can't drive. It's nice and solid and has plenty of room inside. It didn't fit perfectly on my Topeak bike rack though - it overhung the back and I was a bit concerned about it tipping but I used elastic cords to secure it. Would prefer it if there was a way of making the fixing more adjustable so that the bag could be fitted longways or sideways and could allow for different sizes of rack.
This bike bag looks great and is very stable. An added bonus is the bag can be easily removed from the holder.
Our dog is 6.8kg and has plenty of room.
The rack on my bike is a bit too narrow for the bag, but we've solved that problem by adding some foam rubber as a cushion and some velcro for to secure it.