3/8" thread, weighted for balance. Rancilio #10060051.
Note: An additional gasket is required. Click Here to View.
The weight on the top is easily removable, and then this is the direct replacement for Rancilio part #10060059 or 10060061.
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.