I wish I had known about this product years ago, it would have saved my back, time, money on new batteries and a lot of headaches. There was it first for large industrial batteries but not for this type of battery, it was very easy to install anyway, I have three trolling motor batteries and in 1/2 hour everything was in place and ready to go. Just use the hand pump (sold separately) and start pumping water, once the cells are full you can stop pumping water, it's that simple! And just check it out from time to time afterwards to keep it full.