MediumBack: Extra Extra Small: Height: 440 mm / Leg support opening width: 180 mm / Recommended user weight: 12-17 kg|MediumBack: Extra Small: Height: 500 mm /Leg support opening width: 200 mm Recommended user weight: 17-25 kg|MediumBack: Small: Height: 560 mm / Leg support opening width: 270 mm / Recommended user weight: 25-50 kg|MediumBack: Medium: Height: 620 mm / Leg support opening width: 320 mm / Recommended user weight: 45-95 kg|MediumBack: Large: Height: 650 mm / Leg support opening width: 400 mm / Recommended user weight: 90-165 kg|MediumBack: Extra Large: Height: 680 mm / Leg support opening width: 520 mm / Recommended user weight: 160-240 kg|MediumBack: Extra Extra Large: Height: 680 mm / Leg support opening width: 660 mm / Recommended user weight: 230-300 kg|HighBack: Extra Extra Small: Height: 580 mm / Leg support opening width: 180 mm / Recommended user weight: 12-17 kg|HighBack: Extra Small: Height: 680 mm / Leg support opening width: 200 mm / Recommended user weight: 17-25 kg|HighBack: Small: Height: 800 mm / Leg support opening width: 270 mm / Recommended user weight: 25-50 kg|HighBack: Medium: Height: 920 mm / Leg support opening width: 320 mm / Recommended user weight: 45-95 kg|HighBack: Large: Height: 980 mm / Leg support opening width: 400 mm / Recommended user weight: 90-165 kg|HighBack: Extra Large: Height: 980 mm / Leg support opening width: 520 mm / Recommended user weight: 160-240 kg|HighBack: Extra Extra Large: Height: 1000 mm / Leg support opening width: 660 mm / Recommended user weight: 230-300 kg|Maximum user weight: 300 kg