Allbirds Trino Thong Underwear Raincloud Dark Grey Merino Wool Blend Sz 3X NEW New in box Wool blend Dark gray black color The Trino Thong is a thong that features a trim design with a mid-rise waistline and silky-soft seams. It's made with materials like soft merino wool and breezy, silky smooth eucalyptus tree fiber that help minimize odor and wick moisture.