Please fill out the form below for Vertical Reference System and get a quote for part number 501-1854 by L 3 Avionics, please include required quantity along with expected turn around time. Our knowledgeable account manager will reply you shortly. Also check for the related parts for part number 501-1854. ASAP Aerospace distributes nose to tail NSN components, sub-assemblies, and assemblies for the aerospace and aviation industry.