If you're doing any serious casting its highly recommended you use a shock leader. The general rule is, the breaking strain is oz * 10 + 10 for safety. So a 5oz lead would require a 60lb shock leader. The length is usually around 9 metres (30 feet) or 5-10 turns on the spool and then back to the first guide on your rod. Don't worry too much about exact length!
Check out THIS link to learn how to tie a shock leader to your main line. Or otherwise use whats called a "tapered" leader which tapers from 60lb to 18lb.
If you use swivels then your main trace swivel needs to be stronger than the shock leader, so you need to have a trace swivel (preferably a rolling pattern) of size 6 which is 80lb.
Your Lead trace needs to be either equal or stronger than the shock leader also.
<font color='#000000'>depends what u mean by traces if ur talking about the line to the hook then use what u want say 12-20lb or more depending on what species u want and the presentation.
there are just two main types of rigs we use, legers and paternosters. i advise u to look some up on a search engine, but a leger rig is where the weight is sliding on the mainline (shockleader) which u attach the hooklength to the end of - u have all the protection u need with the leader to take the impact.
paternosters are where you have about a metre or so of line with hooklengths coming of it. at the end of ur metre or so of line you attach the weight so therefore ur metre or so of line also needs to be the strength of the shockleader to take the strain when casting.
there are also pully rigs but dont want to confuse u now.
basically when your rig is attached to ur line with the weight on and u lift the rig off the ground, make sure all the line that is tensioned under the weight of ur lead is 50 or 60lb shockleader (50 or 60lb is just a rough gide, 60 is normally all u need)</font>
<font color='#810541'>Trace body and leader ALWAYS to be made out of heavy line, ie the 10lb per oz ratio mentioned above - typically 50lb or 60lb for UK shore fishing with 150grm or 175grm weights. Go 60lb to be safe. My personal choice is for a 'clear' colour - not sure if it makes much difference for 90% of my fishing, but I feel more confident using it.
Regularly inspect trace bodies and leaders for any signs of abrasion. Replace at the first sign of trouble.
Blame the EU buerocrats for (amongst other things) imperial/metric complications - weights used to be sold in ounces and line in lbs, but now weights have 'lost' their ounces and have been replaced by grams. Line usually has both marked on. No wonder it can be so confusing to newbies.
Don't worry if the heavy line isn't marked as 'shock leader' any 50lb/60lb line does the job - in fact big spools of 'normal line' offer better value for money than what is in some cases effectively the same line repackaged as 'shock leader' on smaller and more expensive spools.</font>
<font color='#0000FF'>Myself I believe that normal 60lb line is not right for use as shockleader as it tends to be very stiff, with a high memory and to me it doesnt feel right on the spool. Stick to greased weasel or something along that line.</font>