They look nice, but are extremely loose. - Spikes Tactical Lightweight Chromoly Castle Nut

I purchased both the standard and the lightweight version. The standard castle nuts work fine, but I always dislike that rough phosphate finish. The lightweight fancy ones must be made for spikes by a different company because they are extremely loose on every quality buffer tube ive tried fitting them on. I measured the inside diameter with a caliper, and the inner circumference was significantly larger compared to the standard castle nuts. If you want some fancy billet castle nut, spend the money and grab something else like FCD.