This is standard Hex flange nut following up with ANSI standard to suit for some garden machinary and Our fastener have passed many limit test requirements/quality control before selling out.please check the picture, size and self working condition requirements clearly and choose right spec before you purchase it. Offer reliable after sales-service,please feel free to contact with us if you have any queries need our help.we will reply you soon and let your installation feeling more smoothly.