Adjustable push-in force via a local knob or remote via a Bowden wire.
Single touch releases to allow full extension or the ability to lock it out.
Extended stroke through telescoping mechanisms, usually composed of one rod and two cylinders (the smaller of the two cylinders actually acts as a second rod extending in and out of the larger cylinder).
Vari-lift - intended for short production runs and prototypes, in applications where the exact force is important but hard to estimate in advance, such as lifting a lid slowly in a known time. In this case, the cylinder is supplied filled to maximum design pressure but equipped with a bleed port, to allow gas to be released once installed. The intention is that the design can be over-sprung, and then the pressure reduced in stages, to optimise behaviour. If too much gas is released, a new spring must be installed, and for large quantities, it is better to order a bespoke pressure setting from the maker.