These G 1/4" spacers are nickel plated brass with rubber O-ring and are used in blocks where you need to keep all the threads from hitting the bottom of the block. Especially helpful with GPU blocks.
Spacer OD: 20mm
Spacer ID: 13mm
Materiel: Nickel Plated Brass
Total Thickness: 3mm (without o-ring), ~3.5mm (with uncompressed o-ring)
Fitting Type: Thread Spacer w/recessed o-ring
Quantity: 1 Spacer