4mm/0.2"
10Pc Black Rubber Round Flat Washer Assortment Size 5x21.5x4mm Flat Washer
A nice touch with Safety Technology International is the included installation guide.
30Pc Black Rubber Round Flat Washer Assortment Size 4x9x2.2mm Flat Washer
You will notice the Isoflex NBU 15 keeps its structure even in wet conditions.