1AWG copper ring terminals. You may choose a 5/16" or 3/8" inner diameter ring. 
This 1awg copper terminal is made for 1awg only. It does NOT fit 1/0 or 0 gauge cable which is one size larger than 1awg.
The 5/16" size fits my zinc grounding lugs perfectly and the 3/8" size fits most batteries.
Sold individually.