In terms of mech mods you need to address the concerns that you will have in terms of your vaping style. For example battery life. If you want to be able to get all day use and your a heavy vaper then you will need a mod to that will take a longer mah battery not a 18350 unless you want to be swapping batterys every few hours. As mentioned before getting a telescoping mod is the way to go. I love my ggts and it takes a huge range of batteries. If you looking at one with wires in it then dont buy it because its not a TRUE mech mod. Another thing to consider is performance. At a minimal you want solid brass contacts. I would not get plated contacts unless silver, stainless is ok but not as conductive as brass. If you can find silver plated like on poldiac then thats about the best you can get with the exception of gold plated. Brass is usually the standard and performs well. Be careful of china mods as they tend to use the cheapest material they can find. I damaged the brass firing pin on my ggts and could only find stainless replacement and i can tell the difference, hopefully get a brass on when they are available again. I guess it really comes down to your budget. If you want something nice and have the money to spend i would get a ggts, poldiac, caravela(if you can find someone to sell you one) EA telescoping mod, I hear Precise is nice, Atimizoo, or GP, ect. I just got a piccolo v3 and its freakin nice. with a penelope or spheroid on top it rips hits and last a good bit for me on a 14500 600mah battery. If your on a budget then some of the mid range mods previously mentioned are a good deal. I do find with the more you spend the better quality and performance you will get. Just be careful of china knockoffs, they tend to look nice and perform like crap