Choose a non-porous material. Silicone is the most common: soft, somewhat flexible, and body-friendly. Glass and metal are hard, smooth, and completely non-porous, and they all handle all types of lube. They feel heavier and can be heated or cooled for temperature play, but they are not flexible at all.
Avoid porous materials like PVC, TPE, and TPR in a toy for anal use. They have microscopic cavities that can be cleaned on the surface but not completely, and in a toy that comes into contact with bacteria from the intestine, that’s a drawback.
Icicles No. 47It is a glass plug with three graduated balls, a narrow neck, and a flared base: 9,5 cm insertable and 3,5 cm as widest. The manufacturer states that it can handle the dishwasher and all types of lube. Glass has a downside you should know—it can break if dropped, and a plug with a crack or chip should not be used.