For me, the flex waistband with adjustable button-hole elastic is absolutely essential in kids' pants. Just way too much variation in kids' waist sizes (even between meals--ha, ha!) to be sure of reliable fit otherwise! So I love that these pants have the adjustable waistband plus everything else I want in a little boy pant: sturdy fabric, reinforced knees, a nice classic near-the-waist fit that isn't "girly" fit way hanging down on top of their hip bones (which just makes the pants slide down so kids don't have a full range of motion), and a fairly slim cut that doesn't run baggy or tight. I ordered a pair in both khaki and navy for my son, who just turned six. He is on the taller side for his age, though fairly slim, and I feel these pants run LONG since I needed to order him the 5 for the best fit. The 5 is already almost dragging on the floor when he doesn't have shoes on. A child who is short for his age will really need to size down.