These extremely heavy 80mm diameter leg irons weigh around 3.5 kilos which is around 7.5 pounds.  There is a very good conversion site to be found on http://www.onlineconversion.com/weight_all.htmThese leg irons are usually used on prisoners who have either tried to escape or attacked other prisoners, we imagine.  They are basically the model number 05CHLA with extra weight moulded round the chain.