Ventral Fins add stability in high speed turns, high angles of attack, prevent Tailirons from catching the tips as you flare the landing, look incredibly cool, and are scale. They also help prevent Dutch Roll enhancing directional stability. See research link #1 below. Which may add a few MPH.
These Ventral Fins are very tough, made from .032 ABS black plastic and weigh in at 18 grams.
They will last for a good long while in rough service saving the bottom of your aircraft. They come with a flat black primer coat.
Installation is a snap - you can tape or glue them on before or after paint.
Install so as to match the upper rim of the conformal fin body with the top edge of your belly pan (see picture 4&5). Match the rear edge of the conformal fin body with the front edge of the servo opening making sure your servo arm clears in it's travel. Trim if necessary. This will align them with the slipstream, give you the correct angle and distance from the lip of the intake. The belly pan tapers towards the rear of the aircraft as does the fin body. Mark the overlap and cut a flush seam.