Selling my TempDrop sensor along with 2 armbands: New Fabric Armband (Deep Navy) + Extender for bigger size adjustment × 1 (size L/XL: 12.5-18.5 Inch)-purchased from TempDrop AND another arm band I purchased from Etsy (13 inches) with 2 extra sleeves (polka dot and floral). I found this one to be more comfortable than the one from TempDrop. It’s super stretchy.