Top positive review
I've put 1/2" on my painfully thin forearms in about 7 weeks
on 1 May 2017
Waited a little while before giving this review as I wanted to see if I had the same issue as previous customers have stated with the squeaking. Sure enough, they started squeaking, but a quick spray with wd-40 cured that, and they have been fine ever since (note that the squeaking in no way interferes with the usage, obviously it's annoying to listen to nonetheless).
Delivery: purchased via Amazon Prime so next day as per usual, no issues there, well packaged as you'd expect (both the item itself and the amazon delivery outer packaging).
I'm a 5' 11" male, with not particularly big hands - as you can see in the 3rd picture, the top of the spring is around 5" from the base of the handle, so hopefully that gives some gauge as to the size of them as I noted some others said the grips were too large and I was also a little concerned about that - luckily I needn't have been in my case.
Very comfy to use and non-intrusive, often use them while reading so you aren't going to break out into a sweat anytime soon with them. As for results... well I've been on an exercise kick anyway, so I'm not sure how much these have helped directly, but I can tell you I've put 1/2" on my painfully thin forearms in about 7 weeks of use (started with 10 'flexes' at a time for each hand, now up to 40 with each hand), using them every other day twice a day. Great for bringing the shopping indoors from the car, not so sure my special alone time has been enhanced though.
Any average-sized man should be fine with the size of these grips, and for what it's worth my girlfriend who is 5' 5" found them too big to use comfortably when I asked her to have a test of them, so maybe a smaller size would be better if you are not so tall, or have smaller hands than the 'average' male :-)
minus half a star for the aggro of me getting a can of wd-40 to spray them with, but can't bring myself to only give it 4 stars, so a 5-star review it is.