21.5 mm OD x 6.5 mm ID, 1.8 mm thick, stainless steel - UNI 6593 - DIN 9021 - ISO 7093. For Futurmat, Mariali and other Spanish manufactures valves. For the smaller version use F_473.
WARNING: This product can expose you to chemicals including lead, which are known to the State of California to cause cancer, birth defects, or other reproductive harm. For more information, go to www.p65warnings.ca.gov.