M5 Silicone-Rubber Well Nuts Great for Body Kits and Flares. Until now, we have not been a fan of Well Nuts for body kit usage due to the low-grade rubber most sources use. However, we commissioned a composite version to be produced that is much more durable. The Well Nuts are M5-0.8 thread pitch (works with typical metric M5 fasteners) and the hole-diameter required for use is 9.4mm. Sold in packs of 10