So far just mild steel but very good idea for TIG or gas welding.
Each ring fits inside the tube and aligns the two pipes with a divider. The divider becomes the welding filler. You ring right into the joint which prevents internal slag and alignment issues.
http://www.summitracing.com/search/Part-Type/Exhaust-Tubing-Alignment-Weld-Sleeves/
![hok-12102hkr_w.jpg hok-12102hkr_w.jpg](https://www.lextreme.com/forums/data/attachments/17/17500-8b44323bffdb6f0c9c34dc5568463075.jpg?hash=i0QyO__bbw)
Each ring fits inside the tube and aligns the two pipes with a divider. The divider becomes the welding filler. You ring right into the joint which prevents internal slag and alignment issues.
http://www.summitracing.com/search/Part-Type/Exhaust-Tubing-Alignment-Weld-Sleeves/
![hok-12102hkr_w.jpg hok-12102hkr_w.jpg](https://www.lextreme.com/forums/data/attachments/17/17500-8b44323bffdb6f0c9c34dc5568463075.jpg?hash=i0QyO__bbw)