I have found relic hunting, Hunting Old Houses Sites which are "Super Irony " l smaller Octagon Coil is over best coil. The Smaller Octagon coil still has maintains excellent depth, ground coverage not affected by soil , just like Standard Octagon Coil. The 8 inch Concentric about 2 inch loss in depth Vs Stand Octagon Coil, and also affect more by more Bad Soil and may lower settings less "Hotter Settings "The first signs if soil hunting not good soil is false signals { All Concentrics Coil Affect More Worse Soil} If you hunt modern Sites such School contain lot modern trash {Pull Tags, Foil Ect} 8 Concentric Will Best Coil. Lastly. I have found when hunting with DeepTech I use {Visita X /Gold Hound} in all my Super Iron Sites, The use Iron Volume Control Is Important Feature use it and master it you be surprised! why don't use it more . In Irony I Adjust" Iron Volume " Control Before I Adjust or Lower other Setting { Gain/ Threshold} which many Affect Depth /Audio response Small Super Deep Targets [ Over 12 Inch} . No matter what size coil you hunt with in Super Iron Sites , you must Hunting Slow Super Slow !, and checking each signals different angles is must. Hope Find info helpful.