Compare the options
| Product | Who it suits | Trade-off |
|---|---|---|
 Fresh Step Crystals (full litter) | Choose it for a silica gel litter whose maker states the material outright. | It does not clump. |
 Boxie self-cleaning crystal formula | Choose it for a silica gel crystal that also lists probiotics. | We make no claim for the probiotics, and it is separate from Boxie's clay formulas. |
 Fresh Step Litter Box Scent Crystals (additive, not a litter) | Choose it only if you want added fragrance in the box. | It is an additive, not a full crystal litter: it releases fragrance and is water soluble. |
 Purrify | Carbon granules, not a litter. Our preferred mix-in, and 120g suits most homes. | It works with any litter, crystal included, but it is an additive, so it still needs litter underneath. |
Fresh Step Crystals (full litter)
The maker's FAQ names silica gel as the material and says plainly it is not a clay litter. [1]
Boxie self-cleaning crystal formula
Boxie's ingredients page lists its self-cleaning crystal formula as silica gel with probiotics. [2]
Fresh Step Litter Box Scent Crystals (additive, not a litter)
A Pets People wholesale listing describes Fresh Scent crystals, SKU FFP8990, as a product you mix into litter. It releases fragrance and is water soluble. [3]
Purrify
Carbon granules sold in bags. Sprinkle two tablespoons on fresh litter, mix gently, and add more when the box smells again. No set timetable. [6]
This site may earn a commission when readers buy through affiliate links.
View on PurrifyWhat crystal litter is
Both crystal litters we found maker pages for list silica gel as the material, and Boxie's ingredients page pairs it with probiotics. The name is a start. The ingredient line is a better guide.
[1][2]How it differs from clay and plant litters
The base material is the clearest difference on paper. Fresh Step's Simply Unscented is clumping clay with enhanced carbon, and Boxie's Unscented Natural Clumping Clay Litter is listed as bentonite clay. The crystal litters are listed as silica gel, and Fresh Step says its crystal litter does not clump. World's Best whole-kernel corn litter is a third base. Which base suits your box is a preference to weigh, not a result we measured.
[4][2][1][5]Label and handling checks
Start with the word. A Pets People listing describes Fresh Step Litter Box Scent Crystals as a product you mix into litter, while Fresh Step's FAQ describes Fresh Step Crystals as a full litter, and the two are not interchangeable. Then check the listed material, whether it clumps and the disposal directions on the bag. Fresh Step's clay directions say trash, not flushing, so read the crystal bag's own line.
[3][1][4]What we have not verified
The two Fresh Step products here do different jobs: the full crystal litter is silica gel and does not clump, while the scent crystals are an additive that releases fragrance. Boxie's crystal formula pairs silica gel with probiotics, and its clay formulas are separate products.
Affiliate disclosure: the View on Purrify link is an affiliate link.
[3][6]How we compare
These are desk comparisons. We read what the makers publish, set the products side by side and pick by fit. We have not tested the products ourselves, so the pages report no measured results, no lab figures and no numerical ratings. Every comparison lists its sources.
Sources checked
- Fresh Step FAQ, Crystals full litter (maker) Source read on 2026-10-23
- Boxie ingredients page, crystal formula (maker) Source read on 2026-10-23
- Fresh Step Litter Box Scent Crystals, SKU FFP8990 (Pets People wholesale listing) Source read on 2026-10-23
- Fresh Step Simply Unscented page (maker) Source read on 2026-10-23
- World's Best Multiple Cat Unscented page (maker) Source read on 2026-10-23
- Purrify products Source read on 2026-10-23