In my original review, by clamp, I meant baseplate, where it mounts onto the table. However, when Ugreen support contacted me, they might have mistaken clamp for the phone clamp, and sent this (and i quote): "As regards the material of the clamp, the metal is still and may damage the paint or glass of phones. Please do not worry about it." That doesn't seem to instill confidence in their own product, I wouldn't use a phone without a case, but i know people who do. Hm...original review below.
I just received this today. The build quality is excellent, most of it appears to be machined aluminum or steel, except for the base - that was plastic, and was my first concern for worry, and first "uh-oh" moment. The clamp allows for multiple directions of attachment for the arm, but is again plastic. Plastic which can easily crack, deform, bend, break, especially when exposed to harsher conditions (cold/hot/etc.) The arm itself holds a phone fine, without any issue. Once I put on an ipad, the entire arm started to sag. This isn't some large 12.9" ipad pro, it's a regular ipad 9.7". The arm could not hold the ipad, and tightening the joints did nothing. There was no proper way to "lock" the joints, and the support the springs give is just not enough, and the springs also don't provide consistent force all the way around (ie, at the top, it almost held the ipad, but once the top arm was parallel to the ground, it could not hold). This is a common issue with this type of arm design, and usually requires some sort of adjustable tensioning, that increases support as the load moves farther away from the center axis, and imparts more downards force over the joint. This does not exist on this arm. There isn't even additional support that you could "add" onto the arm out of the box.
The joints, as I've mentioned, are all plastic, and within the 10 minutes I've been setting it up, I've already observed noticeably "peel" and deterioration on the joints.
Extremely dissapointed, and would not recommend. However, if you are dead set on this, buy 2 so that you can "double up" the springs on one, turning the second one into a donor piece.