This hat clip light is amazing it is one bright light I will tell you that. It has 11 super bright LEDS. It fits my husbands hat perfectly and it has not fallen off once. You can use this for fishing and hunting or you can use this in your home for places that are not lit well. My husbands hat is just fine it has not messed up his hat or anything. This light is really helpful and... we have tried other hat lights and none of them have compared to this one. Its great for my husband because when he works on our van he needs to be hands free no more aggravation of others holding the flash light he can see where he needs it. I highly recommend this hat light you wont find another like it and it is only 12.99 on amazon which is a great price. This is a great quality hat light and I am very happy with it. It does take 3 PC AAA Battery (Not Included) Size: 90 x 60 x 17 mm The on/off switch is a button located on the bottom of the light. LED lights are built to last a very long time so you will be able to use this light for a while and when the batteries go dead just buy more. I got my husband this and he is very happy with it our sink was having problems with the plumbing and he was able to fix it using this light and it made the job so much easier for him!!