Tack and harnesses refer to gear used to equip mounts like horses, griffons, or other creatures, including saddles, bridles, reins, and packs, often enchanted or customized for specific terrains, creatures, or magical effects.
As with all equipment, these prices and sizes are standarized towards medium (and small) creature sizes. To apply these to larger creatures, you will often need to use enchantment templates tailored to the mount's size. For example, enchanting a dragon as a mount will differ significantly in cost and complexity compared to a small rabbit.