I bought these to replace the old loose tuners on my 1999 American Standard P bass. There aren't any "drop-in" tuners that fit this model, so some drilling was required.
The tuners themselves are excellent, as you would expect from Gotoh. This was the second type of Gotoh tuners I've installed on a bass; the first being for a headstock-heavy Warwick Thumb, so I knew what to expect. The material is some kind of coated aluminium, so pretty much feels like cold plastic in the hand. Their lightness is indeed surprising, and you might be mistaken for thinking that they're not sturdy or reliable. Definitely not the case. They're smooth, solid and precisely constructed; just what you'd expect from good Japanese engineering. One excellent feature these have is a tension screw on the underside of the tuner shaft, allowing you to increase the turning friction for a nice, consistent tight movement. They also look excellent.
Two things of note: Firstly the ferrules (the cylindrical rings that the tuner posts poke through) are "press-fit", but they were very slightly too small for the holes in my Fender's headstock. On advice from a Talkbass thread, just a few layers of simple masking tape gave them the added diameter they needed for a nice, tight fit, so crisis avoided.
Secondly, as you'll read in other reviews here, take VERY special care with the included screws. They're made of the same aluminium material (testimony to Gotoh's obsession with weight reduction for these tuners!), and so while they're hard, they are softer than regular screw steel. Therefore, they can be stripped very easily if you're using the wrong sized screwdriver head, or overtighten. I was extremely worried about dealing with this, but I can say I got through the entire installation process without stripping one of them, so it's definitely not impossible. The key was to ensure I was using exactly the right sized screwdriver head, screwing carefully by hand to avoid overtightening, and also applying a bit of candle wax to them before screwing them into the pilot holes I'd drilled. If you do these things, they go in just fine, and you won't have to go through the stress that other reviewers describe.
Yes, Gotoh should probably sacrifice the few grams difference between this aluminium material and regular steel screws, so users don't have to deal with these extra precautions. However, I guess that would defeat the purpose of these. You're buying these because they're incredibly light, so Gotoh is taking that philosophy all the way, and I love that.