Check the listing for details. Spa Frog Canister Cap. Condition: New. Listed at 7.50 USD. The Spa Frog Canister Cap is a round cap made of ABS material with a diameter of 4 inches and a height of 2 inches. Designed by Kings Technology, this canister cap is specifically designed for use with SpaFrog products to help maintain water quality in spas and hot tubs. Its compact shape and durable material make it a convenient and reliable option for keeping your spa or hot tub clean and clear.The Spa Frog Canister Cap is a round cap made of ABS material with a diameter of 4 inches and a height of 2 inches. Designed by Kings Technology, this canister cap is specifically designed for use with SpaFrog products to help maintain water quality in spas and hot tubs. Its compact shape and durable material make it a convenient and reliable option for keeping your spa or hot tub clean and clear.