I guess you can consider this a thorough and formal review of the Sunlu S2 dryer box, at least as formal and thorough as it's likely to get on my watch... Before purchasing the S2 unit, I had been running an S1+ for about a year with decent results. The 55C max temp of the S1 was a limiting factor so the S2 seemed like a good and cost-effective option. Sunlu S1+