Almost ten years ago, I bought a 百靈 (around HK$800) but 好唔準 (used mercury one to double check and then I knew 百靈 is useless), called their supplier who told me that it's normal to have +/- 1-2C, which is unacceptable to me. 37C (normal) is a lot different from 39C(fever for sure)! So, I threw it away (唔夠一年)