The size of the open rings refers to the INSIDE diameter of the ring. Click on the items for more detailed information. Pictured: The proper way to open an o-ring. With two pairs of sturdy pliers, bend one end towards you and the other end away from you (ring stays the same diameter). This allows you to close the o-ring (usually) without a gap. DO NOT bend the two openings away from each other. Nickel Plated O-Ring, 1/4" NPOR14$0.10, 12 for $1.00, 50 for $3.60, 144 for $7.20 Nickel Plated O-Ring, 1/2" NPOR12$0.15, 12 for $1.68, 50 for $6.70, 144 for $13.40 Nickel Plated O-Ring, 3/4" NPOR34$0.20, 12 for $2.35, 50 for $9.70, 144 for $19.99 Nickel Plated O-Ring, 1" npor100$0.25, 12 for $2.75, 50 for $11.10, 144 for $22.25 Stainless Steel O-Ring, 12mm ssor12$0.15, 7 for $1.00 Stainless Steel O-Ring, 16mm ssor16$0.20, 6 for $1.00 Stainless Steel O-Ring, 19mm ssor19$0.25, 5 for $1.00 Plastic Open Rings POR$0.65, 3 for $1.50, 24 for $9.99