Yes! The **FacialDefy 3.0** may help improve the appearance of a double chin and define the jawline. It combines **HIFU + RF + Red LED** to support skin tightening, firmness, and collagen production. Results vary depending on whether your double chin is caused by excess fat or loose skin. Please avoid treating directly over the thyroid area. 

If you are just starting, the **FacialDefy 3.0 is a good choice** because it is easier to use while still offering strong facial tightening and lifting support. It combines **HIFU + RF + Red LED**, with 3 HIFU depth settings and 6 RF intensity levels, so you can start gently and gradually adjust based on your comfort. For a beginner who wants a balance of **easy operation + good facial firming results**, I would recommend the **FacialDefy 3.0**. 

For **facial tightening and collagen support**, I would recommend the **FacialDefy 3.0** if you want a more comprehensive treatment. It combines **HIFU + RF + Red LED**, so you get deep HIFU lifting together with RF warming/firming and red-light support in one system. The **FacialDefy 4.0** is a better choice if your priority is more advanced HIFU treatment with multiple depth cartridges and deeper facial/body contouring. So in simple terms: **3.0 = better for multi-technology facial rejuvenation** **4.0 = better for advanced/deeper HIFU lifting and contouring**  

This device does not require you to set a specific temperature in °C or °F. The RF function has adjustable energy levels and normally creates a gentle, comfortable warming sensation, while the HIFU function delivers focused ultrasound energy below the skin. We recommend starting at a low level and increasing gradually based on your comfort. As long as the treatment feels warm and comfortable—not hot or painful—this is generally normal. 

The cartridges do not need to be replaced after a certain number of treatments. Each cartridge is rated for approximately 20,000 shots. Once the cartridge reaches its shot limit, it should be replaced. How long a cartridge lasts depends on your usage frequency. For most home users, a cartridge typically lasts many months before replacement is needed. 

No, you need to hold down the button while using it. 

HIFU 3.0: Each probe can be used 20,000 times. If you need one, you can purchase a replacement probe under the HIFU category. 

You understand correctly. It can be used a total of 20,000 times. After that, the probe needs to be replaced. It can be found under the Beauty Instrument category in the HIFU Instrument section. 

An eye probe is used near the eyes and can be placed on the eyelids or under the eyes. 

You can check the HIFU Instrument category under Beauty Instrument, where HIFU 3.0, HIFU 4.0, and HIFU 5.0 probes are available for sale.