Soft stretchy cotton blend band that stretches over the head with always on 24/7 identification collar which helps prevent lost pets.
Measure your pets neck loosely then decide appropriate size undercollar from the sizing chart. UNDERCOLLAR® is meant to be loose and comfortable!
XS and S are 3/4"" wide. M, L, XL and XXL are 1"" wide. See the chart size picture below.