Wellies is a nickname for Wellington Boots . They are rubber boots used particularly in wet seasons to walk on wet and muddy ground. They are also used during cold weather to keep the legs warm. They are generally made of rubber and have non-slip soles. Heavy duty wellies are useful for farm and garden activities. Measure your calf size for best possible fit. They are different boot lengths such as ankle length, mid-calf and knee-high length. Wide calf and ankle wellies are other classifications.