How many mAh are these?

It is really frustrating that the mAH rating is not printed on the label. And that Amazon does not include it in the product comparison listings. Also Duracell does not show it on the specifications page for the battery. However, If you go to the Duracell website look closely at the picture of the BACK of the package, you will see that they are rated at 2,500 mHA. This high capacity is why I purchased 12 of them. They really are excellent and long lasting. You would think they would want to brag about that. However, the back of the package claims they

Oops, these are the black Duracell rechargeables from China

can these batteries be used for outdoor solar lights

Most outdoor solar lights do use standard rechargeable batteries. You need to verify this on your lights and check if they are using AA or AAA or some non-standard size of NiMh rechargables. If you see removable AA's, then yes, these will work too. HOWEVER - it is a very expensive solution. Garden solar light batteries cost about 1/3 of what these cost and they will have less storage capacity: 800 to 1000 mAH as opposed to these, which I believe are 2,500 mAH. The smaller storage is enough to keep my lights going half the night here in Oregon. I don't really need them to be lit at 3AM. If you do, then be sure you know how to open the battery compartment, verify the size of the batteries on your lights, and go for it. One last consideration - all rechargeable batteries have a finite number of charges before they stop holding a charge. Solar lights discharge and recharge once every day. And they are continually exposed to the elements. This means they will not last as long as rechargeable batteries in indoor appliances that might need a recharge once a month and which are stored indoors.