I like the ksm-66 and the black pepper extract potentiates it, but it also interacts with medications and can cause some to be absorbed more and therefore be at higher levels than what does you expect. So please ch ck to see if your meds interact with black pepper extract.It did interact with a few of mine and made me way too tired and I did have side effects while the ashwagandha was great for relaxing. I just had to time things differently!A big fan of ksm-66 but just raising awareness of black pepper extract since it caused me to have to look into it when I used this brand. Great if you don't take meds I guess! Very high quality!