This set of upper bags meet the new 2024 F-Open rules for sand bags used to guide the forearm. You can use these assemblies to update your current felt lined blocks by machining 3/16” off the faces of your blocks and then drilling and tapping two 8-32 holes as needed to position the sand bags at the top edge of your forearm on the left side and on the bottom edge of your forearm on the right side. Use the two holes (and not the slots) to locate the hole positions.