Higher the number, darker the lens. Lightest commonly available is probably a 3, darkest probably around a 15.
5 is general gas (oxy/acetylene) most people use a 9 - 11 for TIG and MIG.
They're more or less standardised in that most gas goggles take the same size (although there are round and rectangular ones), most drop down masks take the same size. Reactive ones tend to only fit the mask they're designed for.
Ask advice before picking a particular shade.
Yes. An auto mask will make your like much easier. They are wonderful things. Parweld is probably one of the best of the cheaper ones.
I did look at some on flebay but they seem very expensive just for hobby use, also I am not sure if my mig has the conection point for one (Sealey EM130XT), this is all a big learning curve for me and I am in the middle of making a front rack/light guard for my Africa twin (copy of a Ricki cross one) and my only problem is the start of a weld when you move the mask, you move the torch at the same time and end up welding in the wrong place, typical novice stuff I'm sure. Rog.
Not sure what you mean by connection point Rog, they dont require any connections other than the one to the top of your head
Theyll certianly make life easier for you. How about a slightly early Crimbo pressie?
Yes, they sense the light from the arc, or other things sometimes![]()