It seems to be made of incredibly light, but durable materials.
0.3 kg in inventory
-12 kg when equipped
The Agile top is an item that can be equipped in the Body equipment slot. In addition to its weight reducing property it also has reasonable defensive characteristics. Once obtained it is also cheap and easy to replace. This means that it is commonly used for Runecrafting in the Abyss and quests, in addition to Agility.
Equipping the item requires 35 Constitution and 35 Defence. In addition, given that it is obtained by running 250 'perfect' laps of the advanced Barbarian Agility course, players must either have 90 Agility or be able to achieve this level for each of the laps to complete this course. A common method of boosting Agility to earn this item is by using Summer pies (which effectively reduces the requirement to 85 Agility).