I have three ModKat litter boxes for my two furpeople; the liners are wonderful, very tough. You really can't rip these things and neither can kitty. I'll never buy any other litter pans/liners than from ModKat.
Best litterbox ever
Best litter box ever hands down
Work as intended
I have 3 ModKat Flip Top boxes and I replace the liners in each about 1x-2x a year. They hold up well for long periods. If the litter liners are really soiled (I notice some litters work better in them than others) I will wash them, hang to dry and re-use. Really the only time I have to change them out is when they have been clawed up a good bit by the cats. The fit the boxes quite well, although if it was me, I would have added 2 more hooks in the middle to keep them in place. I do notice sometimes they sag a wee bit in the middle where they are not hooked to anything. Overall very pleased with them, they keep the boxes in pristine shape and from being scratched up.