Compatibility between Manfrotto 501PL and 500PLONG with quick release system 577 and MVH500AH - YouTube
PM501 Manfrotto-Type Quick Release Plate with Arca-Swiss Type Clamp for 501PL / RC3 / RC5 / NG Heads - Walmart.com
SmallRig Counterweight Mounting Plate Manfrotto 501PL for Zhiyun Weebill Lab and Crane2 BSS2277 / SYNTEX.TV
Amazon.com : Manfrotto 501PL Rapid Connect Sliding Plate with 1/4'' and 3/8'' Camera Fixing Screws,Black : Tripod Camera Mounts : Electronics
Amazon.com : PM501 Manfrotto Type Quick Release Plate with Arca Swiss Type Clamp Built in Compatible with 501PL / RC3 / RC5 / NG Heads Features ProMediaGear Strap Port, for Video Heads