ALTTIMERY Mini Portable Brass Whistle Emergency Whistle Outdoor Survival Whistle EDC Tool with Key Ring Material: superior brass Length: 1.65inch; Diameter: 0.4 inch Easy to carry, you can put it in a bag and pocket,or hang it on a keychain and backpack zipper with the key ring Special quick airflow design, easy to whistle and make a loud sound in the open air Perfect For Referees Officials, Coaches, Training, Sports, Teacher, Lifeguard, Life-saving, Protection, Hiking, Camping, Wilderness survival, Emergency, etc