Have the PULOX PO-100 received within 2 days. Was surprised at how small and portable it is (fits well in the handbag) very handy nylon bag with carrying strap. Operation is very simple (after two attempts I had the hang of it). Measurement results are 100% with the pulse oximeter my internist match! Since I have COPD and must constantly monitor my blood oxygen content, I now feel perfectly safe. For these reasons, the device is highly recommended !!!!!