I've worn Clip-in hair extensions for more than six years, from very low price ones to highly expensive ones, single drawn hair to double drawn hair, I've tried a lot of Clip-Ins these years. What the key points to determine whether the extension is good or not that is all but its cheaper price, depends on its usage duration (usually, long usage span denotes it has high quality). I would say the one with non-damaging and long lasting usage period with competitive price is the best Clip-In hair extension.
When I met UniWigs first time, I only bought one set of Audrey Extension (EC1803) because I did not know if the quality is exactly same as they described which is double drown virgin remy hair. My concern erased partly when I received the package though I haven't seen how well these hold up/dye/straighten or curl: the hair feels so soft and strong, and I know they'll last a while and held up great. I have very thin long hair due to iron deficiency (wasn't aware I was low on iron but when I started taking iron pills my hair stopped falling out) so I lost a ton of hair. I got the 20 inch in G-2 dark coffee brown. The 18 inch dark brown was my natural length which was still long and 20 inches added some extra length for me. The dark coffee brown matches my medium-dark brown hair with copper undertones perfectly. The extensions look 100% natural! I showed my mom and she was so shocked at the color match and how unnoticeable they were. Falls around belly button on me and I'm 5'3- 1 package was more than enough for my head. If you have very thin hair I think one package might leave you with extra pieces. I saw a lot of people saying to get 2 but maybe that's if you have thick hair or short hair that you want to make longer. I just wanted a little extra length and volume and one set was perfect!
I Straightened them a few times and they still look new (no weird smell or anything) just straighten like my normal hair does. I've purchased three different sets from UniWigs till now. Each of them last nearly one year without damaging (of course you need to maintain and care them regularly and properly), so I'm pretty happy so far and I would say UniWigs has earned my loyalty and their Clip-In Hair Extensions are the BEST!!