Elvie Stride 21mm Breast Shield is the smallest breast shield size available for Elvie Stride, specially designed for nipple widths between 16mm and 18mm. The unique fitting system of the Elvie Stride Breast Shields ensures greater comfort, correct nipple alignment and effective suction when using Elvie Stride. Available in three sizes (21 mm, 24 mm, 28 mm) for your best fit while pumping. The items come with a 90 day warranty and are designed to be used exclusively with Elvie Stride.