Meant for use where you need a strong joint, or where the material used is not strong enough to support a threaded insert. Larger cross dowels provide more bearing surface for a stronger joint, and reduced risk of material failure.
They can also be used for thinner material, where a screw-in nut wouldn't be appropriate.
Threaded holes are located approximately 6mm from the non-slotted end of the two smaller sizes and 10mm from the end of the larger size. Pre-drill size is about 10mm.
Cross dowels are made of steel. All pricing is per piece, with additional discounts for multiple quantities of the same product.