Blued Cut Upholstery Tacks, in 500 gram boxes. The tacks are available in fine or Improved head. As a general rule use the smallest tack you can to avoid damaging the framework. Fine tacks are generally used for fixing calico & top fabrics, the improved heads are better used for fixing webbing and heavy materials. The 6mm tacks are suitable for the most delicate upholstery work. Generally the 10mm & 13mm are most popular, with 16mm being good for securing webbing or use on slightly heavier frames. The 20mm & 25mm are best suited to very heavy work, usually tacking through multiple layers.