These traps were specifically desiged to use mini-ductor type coils. I had mini-ductor coil stock on hand, so I wanted a design that would be produce a higher Q trap than ones made with torroids. However, the design can easily be used with torroids. There is a mounting hole for use with a nylon screw to hold the torroid in place. Also, there are places to add multiple capacitors in parallel in case you needed a custom capacitance to achieve resonance for a particular band.
The trap PCB can easily fit into a small pill bottle for weatherproofing. For temporary field use I often use plastic sanwich bags for weatherproofing.
So far, I have only used these traps to make a multiband End Fed Half Wave Antenna for 40m, 30m and 20m. The performance has been outstanding.
When designing the trap resonance, I used a reactance of 180 ohms for the inductor and capacitor (as stated in the ARRL antena Book) for optimum performance. The resonance point is at the begining of the band you are trying to trap.