Welcome to HCM!
Thanks for posting your query. I am happy to address your questions. Prejoint tablet contains Manganese, Zinc, Copper, Glucosamine
, Methyl Sulfonyl Methane. The options like Kirkland Signature™ Extra Strength contains Glucosamine , Methylsulfonylmethane, Cellulose, Magnesium Polyethylene Glycol
. Nature Made TripleFlex® Triple Strength contains Glucosamine , Chondroitin and MSM. Cosamin ASU is an advanced proprietary formulation that combines NMX1000® avocado/soybean unsaponifiables (ASU) with Cosamin's FCHG49® glucosamine and pharmaceutical-grade TRH122® sodium chondroitin sulfate. All have the similar components but the closest to prejoint are nature made tripleflex with chondroitin with MSM. Hope I have answered your query. If you have any further questions, I will be happy to help. Thanks