I'm looking at getting a free float upper for my Spikes 16" midlength. Some young friends of mine are suggesting a key mod. Are they just for looks or do they serve some purpose. I've been looking at Midwest Industries 9"-12" SS Gen 2 fore ends, with the long oval openings. I don't put much of anything on my fore ends. Just looking for a reasonable priced and light one. These come with 3 rails attachments I think. The prices are in my budget range also.