This Vorfreude Cardiology Stethoscope offers the industry's strongest warranty; Full Lifetime Replacement. Simply contact us from your point of purchase; we will mail a brand new replacement.PressFrequency pinpoints any frequency, within the audible range, by diaphragm pressure with high acoustic sensitivity for superior performance.This Vorfreude Cardiology Stethoscope includes: a replacement diaphragm, 4 replacement ear tips, a solid carry case for replacements, a customizable stethoscope nameplate, a pupil penlight, and penlight batteries included.Patented BiChannel allows binaural flow contained within single master tubing reducing weight.Oversized stainless steel bell with non-chill ring and ergonomic noise cancelling grip increases the audible volume.Hypoallergenic latex free, PBA free, stainless steel, and sterilized at the factory testing facility.Instructions for usel. ChestpieceThe Oversized stainless steel bell with non-chill ring and ergonomic noise cancelling grip increases the audible volume while ensuring a firm grip on the chestpiece. Take care that loose clothing or mechanical watches do not contact the bell housing to avoid audible interference.2. Changing Frequencies Using PressFrequency Diaphragm.This Vorfreude Cardiology Stethoscope diaphragm allows for full audible range focus with PressFrequency. Try varied pressure until the target audible range is reached.A. Low Frequencies:To listen at low frequencies, apply the lightest pressure on the diaphragm.B. High Frequencies:To listen at high frequencies, press the diaphragm firmly on the chestpiece.3. Patented BiChannel Allows Binaural Flow:A. This Vorfreude Cardiology Stethoscope is designed to provide a comfortable fit while acoustically sealing to your ear canal. The binaural are set to accommodate the typical ear canal with comfort tip in the forward direction as shown.