I have used Schauenburg and NTI standard tunnels and NTI Tuff tunnels. In order of traction 1) NTI tuff, 2) Schauenburg,
3)NTI standard. The NTI standards need to be replaced after 5 years of heavy use. The Schauenburgs are in better shape. The NTI tuff are only a couple of years old so can't testify on that one yet. The downside is the Tuff tunnels are expensive. These tunnels are outside from May through October used in 8 classes in 4 days every week plus a couple of trials
I'll be ordering Schauenburgs for my next replacement tunnel.
Karl