Gellwhu Infant Toddler Baby Knee Pad Crawling Safety Protector, Pack of 6 Pairs For 9 months (around 18 lbs.) - 2 years old (as elbow pads) Length 5  Inch ,Knee/elbow pad diameter 3 Inch Elastic fabric: 80% cotton, 20% Spandex Circumference opening 5 Inch Spandex cotton can expand to 6" (if baby's lower thigh larger than 6 Inch, it will be too tight) Package includes  6 pairs