There are several different types of hearing protection on the market some specifically designed for use with firearms, and are electronic, others simply reducing sound level all the time.
Within these two groups there are several different designs.
Starting with those that simply block noise and are static they range from ear muffs like the Howard Leight L1 and the Peltor “Bulls eye” Shotgunner earmuffs, to the gel kind that fit in the ear, but not in the ear channel, Mack’s is one manufacturer that makes both kinds. To the passive ear channel plugs such as the AOSafety at approximately $1:00 and the SoundGear Tactical which are an electronic ear channel plug at $599.
Then there are the electronic muff style, amplifying the sound until a gun goes off, then shutting down the electronics rapidly as the sound level approaches something around 85 decibels, such as the Peltor Tactical 6S , the Proears series, and EHP Products
Performance is the key issue with hearing protection, no matter which type, they should minimize the damage loud noises will do to the hearing. The measure of the performance is expressed in the number of decibels (dB) that the hearing protection will reduce the sound, typically in the range of 25-30 dB for good hearing protection. Anything less than 25 dB is not a good choice, as damage occurs to one’s hearing at levels around 90 dB and over, and gun reports can be in excess of 120 dB depending on the caliber of the cartridge, and the length of the barrel which of course puts the muzzle in closer proximity to the shooter and viewers if short.
Fortunately, most hearing protection at least claims to be in the range that it is effective. The Howard Leight L1 and Peltor “Bulls eye” (a folding earmuff) for example do seem to do the job.
Among the in ear category is the “hear no evil” and “AOSafety” style from Aearo Company of Indianapolis, IN, and the Etymotic Research ER20 ETY-plugs, Howard Leight, 3M, Sure Fire, Plug Safety and others.
Within the in ear channel style there are the simple ear plugs previously mentioned, and ear plugs attached to an under the chin band, such as the Howard Leight QB2HYG (only rated for noise levels of 100 dB or less). Also there are the custom for your ear channel type, some of which are made by taking a wax impression of your ear channel and then making a custom shaped plug for your ear from some silicone like substance. Other lower cost form to the ear type are like the Radians custom molded earplugs which are in the $16-17 range.
Within the electronic hearing protection there is a vast difference in pricing and of course performance, ranging from $20 Sportsmans Guide, to $599 devices that have inputs for MP3 players, FM radios, and radio for military/police communication. Several of the well known brands include Peltor with the 97451, 3MM with the Tekk Protection Work Tunes and Caldwell with $24.99 E-Max
One online store with a variety of styles and types is here and here and here and here
A complete explanation of sound levels and dB can be found here where one can see a 30-06 rifle can reach 171 dB, and here and here