I have had many a pair of jump leads, most of which all had the same two problems even the expensive models that I have owned.
That it the cable clamps are generally useless and the cable size and quality is poor to say the least.
So I set about making up a pair myself, now this it the mK2 model, revised and improved on the first, but the principles are all the same.
Simply put, you need 3 things -
A means of disconnecting and connecting
The reason for the latter it that these are designed to used from one vehicle only.
The leads are 2800 mm long from the Anderson plug to clamp, this is more than enough, but I always figured more is better than not enough
The cable from battery to the first Anderson plug is 0 AWG and is 500 mm long for the positive and 450 mm for the negative
The cable from the Anderson plug to the clamps is 2 AWG again at 2800 mm long
The Anderson plugs are 600v 175 Amp rated.
The cable clamps are MIG welding earthing clamps with revised contacts.
The total cost for this was £80 posted, not including consumables like heat shrink, solder, tools, battery posts (already had for installation) and time.
This may sound high, but for some leads I know will work every time, first time and not need replacing in a long time, i think it's worth it.
I shall right up the full instructions later when i make another set, but for now here is the finished picture.