From central Mexico, Mammillaria elongata is an aptly named clumping thin stemmed cacti. The stems are thin and elongated and offset, soon producing a small clump. It's an excellent choice for a hanging pot. Spines range from gold to red. The gold form is called "Lady Fingers" as it's spines are mostly harmless and lack centrals.
     The one above is a variety called "Copper King". It's been forming a nice clump in my garden. Below is a pink flowered form. The flowers are usually yellow. Below that is a pot full of the gold spined variety.