Wife picked them up last night. At 2am when I got home from work I put 4 in with a couple medium splits. Came down 6 hrs later and stove top was 400 degrees. I left the stove at 550 when I went to bed. Thats pretty darn good performance. All of the bricks were still visible as red hot coals with blue flames coming off. My initial assessment is they won't burn as hot as cord wood but do hold a cooler fire longer. I'll try them again today when I go to work.