Penta bolts have a five-sided pentagon-shaped head offering a minimum level of tamper-resistance. Penta head bolts are commonly used to secure ground lids and manhole covers. Type 316 stainless steel is considered "marine grade". Stainless steel significantly improves resistance to tarnishing or corrosion.DIMENSIONAL ATTRIBUTES Diameter (Nominal): 3/8" Thread Pitch: 16 Length (Nominal): 2"PRODUCT ATTRIBUTES Category: Penta Bolts System of Measurement: Inch Brand: Aspen Fasteners Head Style: Penta Head Drive Style: Tamper-Resistant External Pentagon Drive Thread Direction: Right-Hand Thread Material: Stainless Steel Material Grade: 316 Stainless Steel Coating: Uncoated Origin: Origin Undefined