Review on 🔩 M6 Barrel Bolt Nuts Kit: 4-inch Bolts, 0.49-inch Nuts & Allen Key - 12 Sets for Furniture, Cots, Beds, Crib, Chairs by Shane Black

They work well when you have the right metric drill bits and dowel setting jig. M6 (in the name) - metric size 6.0 mm. You need to buy a drill to drill a hole for the fastener. The barrel enters a hole with a diameter of 10 mm. You must also buy this drill. I tried drilling holes without a template and couldn't. I succeeded with a cross-shaped dowel attachment. The bolts and barrel work together perfectly, holding the two pieces together securely. And they can be taken apart. This system works well if you have 90 degree angles between the pieces to be joined so holes can be drilled.