4.030 340 JE Pistons?????

Anyone know how you would get that size since stock bore 340 is 4.040? I saw a set of forged JE pistons on eBay for 225$ and was confused as to how that would work? Sleeved? Anyhow, looking for some good info. Here’s a item number for them-

8 NEW JE 4.030 CHRYSLER 340 WEDGE FLAT TOP PISTONS w/ PIN mopar sprint car rod M | eBay



Thanks,
Jake