The ASTM International Subcommittee on Recycled Plastics recently approved what it called major "enhancements" to the plastic resin identification code (RIC) system.
The big change? Gone are "chasing arrows," which surrounded numerals from 1 to 7 that defined the resin used in the product's packaging. Now the marking symbol is specified as a solid equilateral triangle around the number.
So pretty much they drew in the lines for the arrows, from my understanding. The reasoning behind this change, according to a news release, is that it "provides for more effective utilization across the stakeholder community, while also addressing recent innovations in polymer applications and multi-layer materials."