Part Number 503SB having (CAGE Code 51469) and FSC 4820 Valves Nonpowered in stock with ready to ship. Get an instant quote for 503SB Valve Check by Simmons Fastener Corp An Amfast. Fill the form below with your desired order quantity, targeted price and the expected order-fulfilment date. Our dedicated account manager will get back to you within 15 minutes.