I've had these for a while now but haven't really had the chance to use them until lately. Little Hotties are a pair of sachets. Each pair is individually wrapped so they cannot be accidently activated as they need to be exposed to the air to work! So shaking the box will not set them all off by accident! So, the sachets are like little bean bags and you take them out of the packet and shake them to activate the heat producing substances inside. I would gently shake/mix the contents in your hand in the air, for about 1 minute. Then put them in your pockets, inside pockets, gloves, slippers, socks or anywhere you like! They will take about 15-20 minutes to gently heat up and they may even get a bit hotter after that if you've shaken/mixed them well enough! Yes they do absolutely retain their heat for 8 hours and more sometimes. I've used them on walking and climbing trips as they keep the chill away from hands and feet brilliantly in my opinion. I use them in my job sometimes too as I work outdoors 50% of the time. I've passed some on to friends and relatives who have all raved about them! The sachets are well made and like material to touch. They feel just right in the hand and there's virtually no weight in them either. Also, I find if you give them a little shake after a few hours in the air it re-energises them and this is the way to make them last over 8 hours! They are brilliant! I will be looking forward to using them this winter if it's anything like the last one! Highly recommended.
Update 17/Oct/2012. . .
I've still got about 20 pairs of these from this box I bought. I used a pair a few days ago and they're still working perfectly! Brilliant product.