We use all sizes of covers. Materials have ranged from flannels to cottons. We do not use any materials that have loose fibers directly on the infant (flannel blankets or crib covers). The volunteers have done a great job. The community support from quilting circles, church groups and families of employees is amazing! The only request that we made was dark backing instead of light colors. Of course the light colors were pretty, but the darker better for the baby

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