Length is adjustable from approximately 16" to 31". Pendant is made of zinc metal alloy and measures approximately 3/4" across. Second photo shows all seven pendants, each sold separately, or save when you buy the full set of seven.
To wear pendant, adjust the slide knots so the the neck cord is big enough to easily fit over your head.
Once in place, you can shorten the length - using both hands, find the two knots at the back of the cord and gently pull on them forward. They will simultaneously slide towards the front as the cord shortens to the desired length.
Once shortened, to make the cord long again, hold the pendant and gently pull down, causing the knots to slide to the back of the cord.