if its for occasional off road/trials riding these proposed types of rear shocks are useable.
if you want more correct off road/trials suspension, you can go to:
https://www.rockshocks.co.uk
or
http://www.falconshockabsorbers.co.uk
they are quite a bit more expensive, but the built quality is not comparable.
they offer both lightweight completely rebuildable shocks.
the first offers non gas charged shocks.(rebuildable yourself!)
the latter offers gas charged shock.(you'll need to get them charged somewhere with to correct amount/type of gas!)
be aware they both will built the shocks to your specific us!:
weight of the bike, rider with full gear weight, terrain, ..........
rock shocks also offers front springs for the same use, as the standard spring are inadequate for of road/trials use.
in the front you will also need to vary the grade of the oil in combination with the these springs.
