This is one of my own personal favorites, not easy to get into and out of but you really feel it working to increase the range of motion you have in the upper back (extension) and shoulders (flexion). Great for helping you finding comfort in yoga postures that require those sorts of openings such as Kapotasana, Urdhva Dhanurasana (Upward Facing Wheel) and Pincha Mayurasana (forearm balance).