Ark Size Chart
Like all ARK chews, it comes in 3 colour-coded toughness levels:
Soft / Standard (Magenta or Red) - recommended for mild chewing, individuals with low oral tone, or individuals with limited jaw strength just learning to bite and chew. These are the softest ones with the most “squishiness” and “give” to them.
XT / Medium Firm (Lime Green or Teal) - XT stands for "Xtra Tough." These are firmer, but still fairly chewy. Recommended for moderate chewers. Or, individuals working on building jaw strength can eventually "graduate" from the soft to the XT.
XXT / Very Firm (Royal Blue or Forest Green) - XXT stands for "Xtra Xtra Tough." These are the most firm and provide the most resistance to the jaw. No chew tool is indestructible, but these are very tough / the longest lasting option for avid chewing. The Y-Chew XXT is usually the overall longest lasting chew for most avid chewers.