For sailors just wanting to update an existing system to a 8:1 system, the primary line assembly comprises two Allen 30mm blocks securely spliced using SK78 Dyneema. The length of the primary line for Standard MkII is approx. 80cm from loop end to the top of the upper block. The length of the primary line for Radial/Standard MkI/4.7 is approx. 70cm from loop end to the top of the upper block. This is so the top block sits at approx. boom height in the 'released off' position to help avoid the blocks getting caught in the gooseneck. If you want any other length (+/- 20cm) just add a note to the order. Lengths are 10cm less for top of kicker attachment.