Winbyoan Saw Blade Bushing Set Saw Blade Adapter Ring, 1 Inch to 20 mm, 1 Inch to 5/8 Inch, 7/8 Inch to 5/8 Inch, 20 mmto 5/8 Inch, 5/8 Inch to 1/2 Inch, Pack of 10 - Amazon.com
50 PACK 630 295 for STIHL CUT OFF SAW BLADE ARBOR ADAPTER RING 1'' to 20mm | eBay