What is the difference between this set and the other coolife luggage sets (b07c2qcb3g, b07cgb217n, b01gnmmq8w)? is it just the shell design?

It's all about the colors, designs, quality and durability of the product. All of Coolife luggage is made from 3 blends of plastic - ABS (Acrylonitrile Butadiene Styrene) which make it more durable and impact resistant than other luggage. If you're like me and want to have your choice of colors and designs for your luggage then that's where the PC (Polycarbornate) comes in. It's easier to work with when you want more choices in color and design. Check out the color and design on the ABS+PC luggage versus the ABC. "Slick".

My handle suddenly stopped working, which doesn’t allow me to use the rolling feature. What should I do?

Dear Customer, Thank you for purchasing our product. This is Blair from COOLIFE customer support center. We sincerely apologize for the inconvenience. please try the following method. If it doesn't work, please let us know and we'll continue to offer help to you. 1) Pull down the interior zipper and make sure the guide of the telescopic handle is not extremely deformed or have any obvious damage. 2) Identify the pins preventing the handle to come out. (Take note the large size and middle size suitcases have 4 pins. And carry-on size only has 2 pins.) 3) Press the button of the handle and spot out which one of the pins is stuck. 4) Push the pin into the small hole and pull the handle. 5) Close the inner zip, so to restore the interior of your luggage. Please click the link below for more details https://www.youtube.com/watch?v=N6w0bSQrwxg For any questions, please feel free to contact us. Our hotline is +1 725-333-1966 and the phone call service is typically available from PST 8:00 A.M. to 4:00 P.M. You can also leave us a voice message if the phone isn't answered. We will give you a callback immediately to assist you. Best regards, Blair Coolife luggage

Is the smaller one true to size? Is it 20in from bottom of Wheels to top of handle?

Dear Rod, Thank you for your inquiry. I am glad to answer it. The suitcase dimensions take the maximum outside as a standard. That means it includes the bottom of wheels to top of the handle when retracted. I hope this resolves your concern. Have a nice day! Best Regards, Coolife Luggage Dean