This is the most comprehensive assembly of Adapters in the industry. All items have passed our engineering inspection to make it into selection. The differences in the various brands are as follows: XRP adapters are 100% machined in the USA from North American alloys. AN Plumbing brand adapters are made in the USA to AS / MS & AN specs and are commonly used in the experimental aircraft. Earls & Goodridge Adapters are globally sourced.