Shop: Chain Link Fence
Generally the commercial and industrial styles of chain link have larger diameter posts and heavier wall pipe for both posts and top rail than residential chain link. We generally use domestically manufactured Schedule 40 or HF40 posts in a 2" or 2-1/2" O.D. If the job is not specified, choosing which is best for a particular application is not always clear. Nearly any weight will hold the fence erect for many years, but thinner wall material will show surface rust sooner. The thinner material tends to have less galvanizing applied during manufacturing. Actual rust through does not occur for many years. In fact I have seen fences of 16 ga. (.065 wall) material still standing just fine after twenty years, even though they are thoroughly rusted outside (and inside).
The top rail is usually 1-5/8" HF40. Seldom is lighter wall top rail used unless the customer is very price conscious. You can save a buck here by using lighter wall pipe or tubing if you prefer. HF20 is a decent choice. It can be obtained in a swedged end, so the use of sleeves to make connections is unnecessary for a little neater appearance, which is only a minor consideration.
Whatever weight material you select, make certain all of your bids on your project are for the same quality material. A good 'deal' on your fence is not a good deal if the material proposed is half of what the competitor offered. It does pay to have a little knowledge of the product you are buying.
Years ago I kept replacing the exhaust pipes on my vehicles every year. On one such occasion, I went to some old muffler guy in a small town and complained of the lack of longevity of my exhaust systems, he took me in the back room, where he bent and fit his own exhaust pipes, and showed me a few different choices in exhaust pipe wall thicknesses. I was amazed at the difference. I was ignorant. I was buying junk all those years because I thought one exhaust pipe was the same as another. I simply bought the cheapest because no one took the time to tell me the difference.
This is true of chain link fence posts and rail also. A thinner wall doesn't necessarily mean it is 'cheap', but you do want to know what you are comparing, besides price. If you choose to use a thinner wall, then specify that to all of your bidders. Likewise demand that all bidders quote on thick wall if that's what you prefer.
This fence illustrates a brace and truss on the end post on the right of the picture. The brace is the center rail and the truss is a diagonally installed, 3/8" threaded rod on a turnbuckle. The purpose is to hold the post plumb. Even though the top rail keeps the two end posts from leaning in towards each other, They can both lean one way or the other, throwing both end posts off plumb. This would be especially bad on gate posts that need to be perfectly plumb for gates to look proper and fit the opening.