I ordered these from the HEMA Shop rather than directly from SPES. This had the main advantage that I could pay with credit card rather than bank transfer. The HEMA Shop has an automated messaging service that does a really good job communicating the status of your order. Postage was reasonably priced and arrived within a week from the UK.
These provide significantly better levels of protection than simple motocross/skateboarding arm protectors, particularly the fact that they wrap completely around the arm to protect the inside of the forearm. This is especially good for longsword.
The plastic inserts are heavy duty and can take punishment. I was initially a little worried that because they are strips with gabs between that blows could land in the gaps, but in action this doesn't happen.
The elasticated velcro of the straps allows you to secure them to your arms providing a close but flexible fit. The straps are also generously long allowing the guard to accommodate a wide variety of padding underneath.
The elbow cup is designed to be worn with a bulky padded garment and doesn't sit brilliantly on a bare arm or over a thin fencing jacket. One of my hopes when purchasing this was that it would help eliminate the need for wearing a bulky padded garment. This, plus my HEMA plastron would provide good protection on the high frequency hitting areas without needing the bulk of a padded garment. It isn't working out brilliantly in this regard.
Significantly more expensive than simple arm protectors, these cost almost $100 including postage compared to $10-$20.
Compared to simple arm protectors they are heavier and bulkier but not unreasonably so and they have little impact on movement.
It's a good purchase and, from what I've seen, is the best forearm protection on the market. On the elbow guard I'm thinking of adding some kind of sock that you push your arm through to better attach it to a bare elbow, but otherwise this is a great bit of kit.