I bought the Hasbro Black Titanium Deathtrooper and Commando Helmet set.
I don't own any of the Hasbro Black 1:6 helmets so the other helmets pictured here are all Hot Toys.
As you can assume, the paint on the Black Helmets is a bit poor. The rear and top of the Deathtrooper helmet is metal; the sides, front, and ranger finder are hard plastic. The whole top of the Commando helmet is metal including the cloth portion. the sides, back, and brim are hard plastic. The Rebel Commando helmet does come with a soft plastic chin strap that's not pictured, I found it in the box after I took pictures.
The stands do come off, the Commando helmet comes off easy, the Deathtrooper helmet requires a bit of side to side force to pop it off. If you want to place a head into the Commando helmet, you'll have to do a lot of modification to the head you want to use such as cutting away the ears and hair/back of the head.
I also own the three figure set of Sideshow Rebel Commando troopers but I don't have the helmets available at the moment to take comparison pics.
Here's pics, the Imperial Stormtrooper helmet is from the HT Luke Skywalker in Stormtrooper disguise and the First Order Stormtrooper helmet is from the HT Riot Control Stormtrooper.
