Corrosion Resistant, Fully Waterproof Vinyl, Made by an OEM Supplier, Multi-Hole Mounting Pattern. * Does Not Have Drain Hole. * Use 4 each 5/16x3/4"NC bolts 18 TPI (NOT included). * The OEM applications that used this seat might have used either SAE or Metric mounting bolts. This replacement seat uses only SAE bolts. Do not reuse original Metric bolts. Damage to the threaded inserts will occur. * As this bulletin covers many different part numbers of seats, you will need to determine exactly what size bolts your specific seat and application will need. The threads will either be 5/16-18, or 3/8-16 and some seats could use either depending on which mounting bolt pattern used.