Another good option - ERGO Modular Wedgelok Rail Covers

These are a good option to choose from. BCM, B5 and Magpul all make mlok panels that are similar in price and this is another good option to choose from.

I bought these for 16 dollars. They look good and feel good. These are made out of rubber instead of plastic and have a tacky rubber feel to them and have a little bit of give aswell. If you wear gloves when you shoot these really allow you to pull the rifle into your shoulder, better than the other options imo due to the rubber design, the bad part is since its rubber, the grippyness will fade with time, im sure of it.

They were kind of a pain to install, which is also a good thing meaning they wont accidently fall off or tear off the gun, you might ruin them trying to take them off idk so make sure whatever youre putting them on, thats their permanent home. I hade to use a butter knife to jimmy them into place.

Idk why they sell these in packs of 4, if you use 2 on a rifle then you have 2 left over for another rifle which is great but if you use them at the 3/6/9 position, like most will, then you have one left over and you have to buy a whole new pack. They should really sell these in packs of 3 for 12 dollars. Makes more sense

Overall these are recommended from me. The advantage these have over other options is the fact they are made from rubber and imo have better grippyness than the competition allowing you to really pull the rifle back into your shoulder.