Shoe trees come in a variety of styles, from simple toe and heel-shaped blocks, separated with an extendable rod, to full blocks that are hand carved to take the shape of a foot. Each style has its own benefits. Fully formed shoe trees are often best at holding a shoe's shape, while a style with separate toe and heel components tends to cost less.
Advanced style shoe trees contain adjustable components, which allow you to extend the length and adjust the width of the toes to better fill out your shoes.
Shoe trees for boots also contain a vertical component that helps to fill out the leg of taller boots. As with their counterparts, you can find boot trees fully formed into the shape of a foot, as well as the ankle and lower leg to give footwear like cowboy boots a good form-holding opportunity. There are lower-profile styles of boot trees suitable for footwear like hiking boots and chukkas as well.