for sliders, i would advise one to get Woodcraft or Yoyodyne.
the shorter the slider the better.
the longer sliders, either snag on sh1t and bend and do frame damage, or they hitch during a slide and send the bike into a flip.
the fact is, most drops will result in bodywork damage, so theyre not really protecting plastics, they're main purpose it to keep hard parts off the ground. frame, case covers, controls.

So anything sticking out more than 2" id avoid. i have yoydynes, and tho theyre a tad long, they have a wide slider that actually slides really well. and can be converted to tie downs.

no cut sliders from what ive seen dont work, as the bracket that they mount to always tends to snap and puncture the case cover. busted or grinded case covers usually = not riding home.
busted plastics, = you ok? yesh? fukit lets go. vroom vroom.

just my $0.02