The X3 harpoon is Scorpena's top model within Rollerguns.
This speargun has an adjustable trigger, so the trigger sensitivity can be adjusted to suit you.
The advantages of a rollergun are that you get a much softer recoil and therefore more precision as the gun does not move as much.
The force is greater in a rollergun as the elastic utilizes the entire length of the spear, whereas a traditional speargun only utilizes 2/3 of the spear's length. 
 
 
Technical information for Scorpena X3
Barrel
Ø 28 mm;   aluminum + polyurethane
Guideline
 Polyurethane, along its entire length
Muzzle
Roller
Harpoon
Ø 7 mm; steel 17-4PH; sharkfins
Speartip
Fixed; 1 barb
Rubbers
Ø 17,5 mm; one piece
Ability to install additional rubber
Yes
Wishbone 1
Dyneema
Wishbone 2
Wire
Loading pad
Yes
Place for the reel
Yes 
Line release
Active, on the right side
Safety catch
Yes
Trigger adjustment
Yes