Rail End Socket (4 types, 10 sizes)

thingiverse

Four designs for round rail end support/bracket/socket in 10 sizes: 13mm 16mm 19mm 21.5mm 24mm 25.4mm 29mm 32mm 40mm 50mm I recommend doing a quick print of the size you need to check for fit, making any scale alterations that are required and then printing with an infill level that matches the application. Although there is now a heavy duty version available, please check suitability if you are using them for particularly critical applications.