This includes the two main parts of the adjustable arm, thumbscrew, plastic washer, and rubber washer for the Umbra Standard support.
This arm is the only difference between the Umbra Standard and the Umbra Short or Umbra Tall. If you have a Short or Tall, you can purchase this arm to convert it to a Standard.
I have used this support for a while and it is very comfortable and versatile for different size players. I changed my posture over a period of time and changed from the short support to the standard length by swapping out the arm to accommodate this. The way the support attaches is so convenient and the folded down unit fits in a guitar case. I continue to be happy with this product and would recommend it.
I am an adult with shorter stature (65in). I tried a support which used suction cups and found that my classical guitar sat too high - the upper bout was near my chin. I bought the Umbra Short support and I gave it a 5* review - so much better RE lower back and hip discomfort as compared with footrest. However, the neck of the guitar was placed at a lower angle and I had to externally rotate the left wrist uncomfortably - this became apparent after a few weeks playing. I replaced the Short arm with the Standard arm and then removed the very short curved arm which attaches to the lower bout - there are pre-drilled holes to re-attach the magnet. This has allowed better placement overall - the upper bout sits just below the manubrium (the bony joint at the upper sternum) and the neck angle allows for the left hand to approach the neck without unnatural rotation of the wrist - closer to 45degrees. In summary, the Standard support is very adjustable and I believe this allows for very successful positioning of the classical guitar for a short stature adult (65in).