Reference the Parker o-rings size chart to help determine the size for your application. 
 
1150-1302 Parker 2-011 Bunan, Safety Valves, 6 Pieces
1150-1303 Parker 2-006 Bunan, Butane Regulator, 6 Pieces
1150-1306 Parker 2-012 Viton, ID 9.7mm, Piston, 4 Pieces
1150-1309 Parket 2-013 Viton, ID 11mm, Piston, 4 Pieces
1150-1318 Parker 2-014, Viton, ID 12.7mm, Piston, 4 Pieces