I purchased this to replace my Tacwise Z1-140, as I needed to fire staples larger than the Z1-140 could handle.
This stapler is fantastic as it takes staples ranging from 6 to 14mm, and has a slider which allows you to increase or decrease the depth of the staple in the workpiece.
Staples are loaded quite simply, by pulling up the end of the staple loader, inserting the staples, pushing the loader against them and clicking it back into position.
The build is high quality, consisting of almost all aluminium, and looks like it will stand up to strong abuse. The only bits of plastic I can see are the handle (reinforced with aluminium), the depth slider and one end of the staple loader.
The handle has a lock on it, but it's not great. The handle locks by pressing it until it comes within range of a metal clip, and hooking the clip onto it. This prevents the handle from springing out, to allow easier storage, but does not prevent the gun from firing. Therefore, this could be a safety concern. It also does not have a belt clip, which is quite a useful feature for staple guns.
If the lock actually prevented the gun from firing, I would rate this at 5 stars.
This review is also available on Amazon: https://www.amazon.co.uk/review/R2OMOTT3O30H3E/ref=cm_cr_rdp_perm