Once you inserted the batteries in the right way (ie in the opposite direction indicated +/- signs ...) Lamp works. UV gel dries quickly, and I do not use the gel at Grüv and it works very well. We just put the finger 2 by 2 for speed. No timer, just an On / Off button on the front, you need a watch to time. No manual, a video on Youtube:
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This product is well designed, attractive and super convenient, but the quality of materials, including plastic, could be better. Nevertheless, it fits in a toilet bag (other lamps are just TOO big), the LEDs do not change and are more powerful UV.