These are very nice and handy little carabiner clips. I initially purchased a set of two Size #1 S-Biners as part of several different items I wanted to try out along with several other products in my search for the most suitable combination of rings and clips to organize my keys. My original thought was to use them to either attach keys or key rings as well as other EDC (Every Day Carry) essentials, but I wasn't careful enough in ordering this and didn't realize the small size until I received them. What I've since learned is that Nite Ize produces these S-Biners in various sizes and materials and finishes. I ended up purchasing several different sizes, and each is suitable for certain purposes. They're all well made, and I think these are a good value. I also like the locking models that are also available (see the models at the bottom of the listing below). After going through a mini research project of my own in order to both determine the relevant dimensions of the various sizes, as well as find the best listings for them on Amazon, here is a guide to simplify this process for others. IMPORTANT NOTES: - I've done my best in determining representative listings here on Amazon for each of these models, but please keep in mind that these are sold by a variety of sellers here, there are multiple listings for the various different sizes and finishes, and the listings are not always well described such that you can be sure that you'll receive the correct size listed. - The prices also vary widely and from my own observations of the various listings here on Amazon, the best prices are for the Amazon 'Add-on Item' listings. It is sometimes necessary to take care in going through the choices available on some of the product pages in order to find those listings and prices. After going through all of this myself, the following listings links are correct as best I can determine at the time of posting this review: --S-Biner, Size #.5, SBHLF-2PK-01 : (available in stainless steel or black, 2-packs) Dimensions: 1.31" x 0.48" x 0.22" | 33.41mm x 12.40mm x 5.74mm Weight: 0.11oz | 3.00g Weight Rating: 3 lb. --S-Biner, Size #1 : (available in stainless steel or black, single-packs or 2-packs, part number begins with SB1) Dimensions: 1.56" x 0.62" x 0.21" | 39.67mm x 15.86mm x 5.50mm Weight: 0.14oz | 4.00g Weight Rating: 5 lb. --S-Biner Size #2 : (available in stainless steel or black, single-packs, part number begins with SB2) Dimensions: 1.95" x 0.85" x 0.24" | 49.75mm x 21.71mm x 6.15mm Weight: 0.25oz | 7.00g Weight Rating: 10 lb. --S-Biner Size #3 : (available in stainless steel or black, single-packs, part number begins with SB3) Dimensions: 2.67" x 1.18" x 0.26" | 67.97mm x 30.09mm x 6.83mm Weight: 0.49oz | 14.00g Weight Rating: 25 lb. --S-Biner, Size #4 : (available in stainless steel or black, single-packs, part number begins with SB4) Dimensions: 3.52" x 1.57" x 0.31" | 89.41mm x 39.92mm x 7.94mm Weight: 1.06oz | 30.00g Weight Rating: 75 lb. --S-Biner, Size #5 : (available in stainless steel or black, single-packs, part number begins with SB5) Dimensions: 4.38" x 1.93" x 0.33" | 111.41mm x 49.19mm x 8.45mm Weight: 1.69oz | 48.00g Weight Rating: 100 lb. ThisNite Ize S-Biner 3-Pack is also available and includes one each of sizes 2, 3 and 4, in either stainless steel or black. (Part number begins with SB234). This is a better value if you want to get these particular size S-Biner's. There are also a couple of variants to the S-Biner product that incorporate locking features to better secure the two gates and prevent them from accidentally being opened: Nite Ize S-Biner SlideLock (size #2 or size #4) (Part number begins with LSB2 or LSB4 for size 2 or size 4) Nite Ize S-Biner MicroLock (size is between the regular S-Biner size #.5 and #1) (Part number begins with LSBM) Nite Ize also offers the same style product but manufactured in plastic, in sizes 0, 2, 4, 6, 8 and 10, in various colors. For example, here is theNite Ize SBP4-03-01BG black #4 size plastic S-Biner . I can't include listings to more of the plastic models here because Amazon limits the number of links to 10 in any review. The size and weight ratings for the plastic models are comparable to the metal S-Biner's. Nite Ize has a very broad product line of hardware products, and it's helpful to go to their own website in order to get the best descriptions of their products as well as representative MSRP pricing, before making final purchasing decisions here on Amazon.