im guessing that's one of those 30 Inch Arms?

And here's the opposite, a Nema mounted on a long double guyed arm

Ever seen 20 foot truss arms with NEMA buckets? LOTS of them around here!

i've never seen arms near as long as the one's jace has in his area....the longest arms in my area are about the same as the one in my pic you linked joe...which i speculate is at least 15 Feet?

the Long Arms in my area are typically guy-wired...and there is a Variety...some of the pretty old ones are straight!...and we gots lots of those in my area and most have so much rust on them,other types are single guy wire and double guy wire...there's also the forked variety,and some other cities use Truss-Arms on wood poles which looks pretty cool's,Truss arm's look clean and are probably the strongest arm i bet.

The logest in my area are 10-12 foot truss arms

Streetlight98...on wooden poles? Where are they?

Yep 30 inches sounds right, the largest arms we currently install are 10 ft tapered Es

Yes, on wooden. They're used throughout Rhode Island

Oh yeah I've seen those truss arms they are 10 footers....I also saw 6 foot bottom praced upsweeps and 6 foot tapered arms in RI too

Yep, we have lots of 8 and 10 foot bottom-braced upsweeps here too. The currently used arms follow:

6 Foot: tapered E; cantelever; non-braced upsweep, braced upsweep
8 Foot: tapered E; possibly some truss, braced upsweep
10 Foot: Truss arms

The Truss arms the 10 foot ones in your area is very much like my areas 10 foot truss arms except small difference...the mounting bracket is different...also my electric company has a few Tapered arms about 8 foot...and they are rare.....they were really old installations and only seen them hold clamshells...haven't found one with cobrahead on wooden poles

All the 8 foot tapered E brackets hold M-250r2's (250w HPS) There are no MH streetlights or utility owned floodlights in RI