large 44mm 1 75 inch opening for easy filling and pouring double wall insulated keeps drinks cold for approx 20 hours iced drinks will keep cold for up to 40 hours available in brushed stainless or mirrored finish made with 188 food grade stainless steel 100 stainless steel interior no taste lingering coatings or lining stainless steel threads on cap and neck stainless unibody cap with sustainably harvested bamboo strong and durable with the highest quality safe non to