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. 

1. After cleaning the face, apply a medium to the skin. It is recommended to use the skin care products you often use, such as lotion, aloe vera gel, etc. as the medium. (Essential oils and essences containing alcohol are not suitable for use) 2. After adjusting the HIFU and RF energy to the highest level that feels comfortable.Use the lifting and holding techniques. The Face treatment use time is 15–45 minutes. The eye area use time is 10-15 minutes.(Ultrasonic waves are not visible to the naked eye. If you need to test whether ultrasonic waves are working properly, you can fill the container with water for testing.) 3. Clean the facial skin with water and apply a moisturizing mask. For better results, we suggest using a mask cover to promote the absorption of the moisturizing mask For deep wrinkles: 15 sessions per course Time of use:Use every 7–10 days For sensitive skin: use every 15–20 days  

You can contact them via email. I recall they offer a one-year warranty. Hopefully, this information will stay with you.